Silver Mine Area

1.Myoshoji Temple

Myoshoji is a small Nichiren Buddhist temple that stands along the Ginzan River walking path overlooking the Ginzancho settlement. It was founded here in 1514 and attracted worshipers particularly from among the merchants of Iwami Ginzan, many of whom were drawn to the Nichiren school’s teachings that encourage the pursuit of spiritual and material rewards in this world as well as in the next. The popularity of Myoshoji endured for hundreds of years, as evidenced by its large mountainside cemetery where the graves date from the 1500s to the twentieth century. Both the temple and its graveyard suffered severe damage in a 1943 flood and series of landslides that devastated the surroundings, but they were later rebuilt. The small, modern cemetery in front of the temple building holds only a fraction of the graves, most of which are hidden underneath trees and bushes on the hillside.

2.Monument to Okubo Nagayasu

When the warlord Tokugawa Ieyasu (1543–1616), now known as the founder of the Tokugawa shogunate that ruled Japan from 1603 to 1867, gained control over Iwami Ginzan in 1600, he appointed Okubo Nagayasu (1545–1613), one of his most trusted allies, to supervise the mine. Okubo was known as a skilled administrator and expert on mining matters. He developed several productive mine shafts, including the Okubo shaft that now bears his name, and is credited with laying the foundations for the mine’s greatest period of prosperity.

Okubo impressed Ieyasu, who later promoted him to supervisor of many of the realm’s most plentiful sources of precious metals, including the gold mines of Sado Island (off the coast of present-day Niigata Prefecture) and Izu (Shizuoka Prefecture).

Upon his death at the age of 69, Okubo had already had several impressive tombs—monuments rather than actual repositories for remains—constructed for himself. But then something unexpected happened: Okubo was posthumously charged with embezzlement and treason. His seven sons and many other followers were forced to kill themselves, and his entire estate was seized. The accusations may have been politically motivated, but no matter: thereafter, monuments to him were either removed or ignored.

Only in 1794 did the people of Iwami Ginzan feel comfortable enough to erect the new tombstone, which stands today.

3.Site of Daianji Temple

Daianji Temple was a Jodo (Pure Land) Buddhist sanctuary founded in 1605 to serve as the future burial site of Okubo Nagayasu (1545–1613), the first government-appointed magistrate overseeing the Iwami Ginzan silver mine. A skilled administrator and expert on mining matters, Okubo was assigned to this position soon after the warlord Tokugawa Ieyasu (1543–1616), the founder of the Tokugawa shogunate that ruled Japan from 1603 to 1867, gained control over the mine in 1600. Okubo is credited with laying the foundations for the mine’s greatest period of prosperity, and was later promoted to a position that involved the supervision of many of the realm’s most plentiful sources of precious metals.

Okubo’s tomb at Daianji—a monument rather than an actual repository for remains—was prepared long before his death at the age of 69. A cemetery later developed around the tomb, as more and more local people chose to be buried on the grounds that honored the famous magistrate. The temple endured until 1943, when heavy flooding and a series of landslides destroyed its buildings. Only part of the graveyard, including Okubo’s tombstone, remains today and can be visited by climbing the stone staircase from the Ginzan River walking path.

4.Shimogawara Smelting Site

The Shimogawara site on the outskirts of the town of Omori was one of the most significant local centers for processing silver ore in the early 1600s. Small-scale dressing, smelting, and refining was conducted near mining sites throughout the area during this period—the height of silver production at Iwami Ginzan—but here the entire process was centralized and more advanced than in the mining settlements up on Mt. Sennoyama. This suggests that the Shimogawara site was run directly by the magistrate’s office, which represented the central government at Iwami Ginzan and supervised the silver mine.

Ore brought here from the mine was first dressed by crushing it and sifting through the resulting stones to isolate the silver-containing bits. These were then processed using the haifuki (cupellation) method of refining, which had been introduced to Iwami Ginzan from the Korean peninsula in 1533 and was the key to producing high-quality silver in large quantities. In very simple terms, haifuki involves smelting copper-containing silver ore together with lead. The silver binds to the lead, forming an alloy. This alloy is then placed on a bed of ash and heated to as high as 850°C while bellows are used to keep the mixture oxidized. The other elements of the alloy eventually melt and are absorbed by the ash, leaving only pure silver. This process was conducted around the clock at Shimogawara, where the buildings likely had fire-resistant earthen walls. The structures also featured high ceilings, several windows, and chimneys in every room to let out smoke and sulfurous gases.

5.Toyosaka Shrine

Iwami Ginzan Silver Mine was controlled by local warlords from its discovery in 1527 until the beginning of the seventeenth century. At one time the silver mine was ruled by the powerful Mohri family based in this area. To mark his capture of the mine in 1562, Mohri Motonari (1497–1571), the head of the family, built a simple temple on a slope above the Ginzan River and installed a wooden likeness of himself within the temple’s main hall.

After the warlord Tokugawa Ieyasu (1543–1616) conquered all of Japan and established a central government in Edo (present-day Tokyo) in 1603, his shogunate assumed direct control of the silver mine. The Mohri territory was greatly reduced, confined to the province of Choshu at the western end of Honshu. Motonari’s sanctuary presided quietly over the Iwami Ginzan area for centuries under the Tokugawa, until war again encroached upon the silver mine. In 1866 advancing troops from Choshu and Satsuma (in Kyushu) came across the temple. The Choshu soldiers, who were fighting against the Tokugawa forces in a conflict that would eventually bring about the end of the era of the shogunate, were delighted to find a statue of their legendary general inside.

Ultimately, after the anti-shogunate forces won the war, the Choshu men built a new sanctuary on the same site—a Shinto shrine this time, in keeping with the new government’s policy of cultivating the native religion as a vehicle of modern nationalism. In 1943, the Toyosaka Shrine was partially engulfed by a landslide, but the ornate gate, the distinctive main sanctuary (honden), and the worship hall (haiden) survive today. The original Mohri Motonari figurine is sadly no longer present.

6.Monument to Prayers for the Prosperity of Iwami Ginzan

The site of what was once Ryushoji Temple is now a quiet grove at the end of a dirt road, along which little more than a single stone monument reminds visitors of the place’s illustrious past. The inscription on the monument reads “place of prayers for the prosperity of Iwami Ginzan”—an indication that Ryushoji was one of three religious sites chosen for an annual ritual to pray for a prosperous year of mining. This ceremony took place on the twentieth day of the new year and involved the magistrate (the central government’s representative at Iwami Ginzan) visiting Ryushoji, Sahimeyama Shrine in Kobuyamadani, and Kanzeonji Temple in the town of Omori to conduct prayers. Why these three sanctuaries were chosen is not entirely clear, but they all appear to have enjoyed the favor of the magistrate’s office. The selection of Ryushoji, a Soto Zen temple, Sahimeyama, a Shinto shrine, and Kanzeonji, a Shingon Buddhist institution, also appears to reflect the religious diversity of Iwami Ginzan, the population of which was varied in terms of both geographical origins and social background.

7.Shimizudani Refinery Site

Now little more than stone and concrete foundations on a hillside, the site of the Shimizudani Refinery tells the story of a bold but failed attempt to restart silver production here in the late nineteenth century. In 1886, when the Osaka-based Fujita-gumi corporation acquired rights to Iwami Ginzan, the mine had already been dormant for decades.

Fujita-gumi invested heavily, introducing cutting-edge mining equipment and methods, including using dynamite to expand existing shafts and extract large amounts of ore. These modernization efforts culminated in the 1895 opening of a new refinery employing the latest technology to process the vast volume of ore Fujita-gumi mined in shafts nearby.

After more than 350 years of mining, the silver deposits at Iwami Ginzan were already depleted, however, meaning that the quality of the ore was lower than expected. The technology used to extract the silver, moreover, did not meet expectations. The Shimizudani Refinery operated for only a year and a half before closing. Fujita-gumi sought to cut its losses by transferring the refining equipment to other mines under its control, including those at Jiufen in Taiwan, which was a Japanese colony at the time.

The foundations that remain today only hint at the facility’s once impressive scale.

8.Shinkiri Mine Tunnel

Routing water out of the silver mine was one of the greatest challenges for miners throughout the history of Iwami Ginzan. As mining tunnels were made longer and deeper, they would inevitably hit pockets of groundwater in the rock and flood, impeding the extraction of ore. By the early 1700s, the groundwater problem had become so severe that the local magistrate’s office, which represented the central government in Edo (present-day Tokyo), had to take action to maintain the viability of the mine. The solution was to dig two new parallel tunnels at an elevation lower than any existing mining sites. Water would flow down into these new interconnected tunnels via shafts and be released into a river. This ambitious undertaking, called the Shinkiri (“New Cut,” as the tunnels cut horizontally through the base of the mountain), was financed with a government loan and completed in the 1720s.

The Shinkiri project was a success: the water release system allowed for the discovery of new silver veins and more efficient mining in existing tunnels. Veins were also found within the Shinkiri tunnels, one of which came to be mined while the other performed water release and ventilation functions. Silver production at Iwami Ginzan increased significantly as a result, if only for a limited period. Though the Shinkiri tunnels have been left all but untouched for nearly a century, they still gather water and release it into the Ginzan River, hinting at the builders’ engineering prowess.

9.Tomb of Yoshioka Izumo

On a forested hillside high above the Ginzan River stands the lone tomb of a man who played a significant part in boosting silver and gold mining throughout Japan in the early 1600s. Born in the province of Izumi (near present-day Osaka), Yoshioka Hayato initially worked as a mine official at Iwami Ginzan under the Mohri family, which controlled the silver mine from 1562. When the warlord Tokugawa Ieyasu (1543–1616), now known as the founder of the Tokugawa shogunate that ruled Japan from 1603 to 1867, gained control over Iwami Ginzan in 1600, he appointed Okubo Nagayasu (1545–1613), one of his most trusted allies, to supervise the mine. A skilled administrator who left politics to the politicians, Okubo recruited Yoshioka, who was valued for his management skills and ability to locate silver veins.

Okubo sent Yoshioka on assignments to several mines administered by the shogunate, including the silver mines of Izu (in present-day Shizuoka Prefecture) and the Aikawa gold and silver mine on Sado Island (Niigata Prefecture). He produced impressive results, which earned him fame, fortune, and the honorary name Izumo, after the province located east of Iwami Ginzan. When Yoshioka Izumo died in 1614, he was buried at Gokurakuji Temple, one of the most prestigious sites of worship in the area. Gokurakuji is long gone, but the tombstone of Yoshioka Izumo—re-erected by his descendants in 1813—remains on the former site of the temple cemetery.

10.Fukujinyama Mine Tunnel

Fukujinyama is one of the top tunnel systems at Iwami Ginzan in terms of the quantity of silver extracted. It consists of three tunnels: two that are interconnected and pass underneath the Ginzan River toward Mt. Sennoyama, the center of the mine, and a ventilation tunnel directly above them. Located along the road to Ryugenji, the only mine tunnel at Iwami Ginzan open to visitors year-round, Fukujinyama cannot be entered but merits attention for a different reason: its history demonstrates how ownership and management patterns at the silver mine changed as production began to decline in the 1700s.

The tunnel was dug by an independent prospector, who chose the spot, received permission to excavate from the magistrate’s office that administered the mine, and financed the project himself. After proving his ability to make the required contributions of silver to the magistrate, the prospector was granted property rights to the tunnel. This arrangement was common during the 1600s, when the silver mine flourished and tunnel owners were able to make a profit despite the significant level of investment required for maintenance. By the 1700s, however, most of the accessible silver deposits had been depleted and profitability declined. Many of the tunnels still considered viable, including Fukujinyama, were acquired by the magistrate’s office using public funds, which were also used to finance the tunnels’ operation. This partial “nationalization” of the mine was accompanied by a range of public works projects aimed at increasing silver output, but ultimately it failed to restore Iwami Ginzan to its former glory.

11.Takahashi House

The Takahashi House sits just off the road to the Ryugenji mine shaft. Its location reflects the significant role that the Takahashi family played in the local mining community. In 1839, the mine operators at Iwami Ginzan elected Takahashi Tomisaburo, the head of the family at the time, to serve as liaison between the miners and the local magistrate’s office, which represented the central government in Edo (present-day Tokyo). This was a key post, as it involved mediating between the mining companies and the government representatives who were charged with hiring the businesses, issuing licenses to work in the mine, and overseeing the silver supply to ensure its safe delivery to Edo.

Through their involvement in the management of the mine, the Takahashi family eventually accumulated a fortune sizeable enough to build one of the largest and most lavish houses in the area. Completed around 1872, it includes the main house facing the road, a teahouse in the garden, and a detached cottage in the back. While not currently open to the public, the Takahashi House allows you to imagine how a wealthy miner and his family lived in an era when silver production at Iwami Ginzan was just entering the modern era.

12.Ryugenji Mine Shaft

Ryugenji is the most significant of the more than 900 mine shafts that have been discovered at Iwami Ginzan. One of the top five in terms of the quantity of silver extracted, it is about 600 meters long, with the first 273 meters now open to visitors year-round. The shaft was dug in 1715 and placed under the administration of the local magistrate, who was appointed by the central government in Edo (present-day Tokyo). The silver mined at Ryugenji was a direct source of income for the Tokugawa shogunate, which ruled Japan between 1603 and 1867.

Several smaller shafts branch out from the main tunnel. These were dug to follow the veins of silver, traces of which are still visible here and there along the walls. The secondary shafts are much narrower than the main passage, which was expanded in the latter half of the nineteenth century to accommodate carts. Mine shafts that predate the introduction of modern drilling equipment are very narrow. The tunnels were dug using only chisels and hammers, which was extremely time-consuming, so they are just wide enough for miners to squeeze through.

As you leave, using the exit tunnel dug in 1989 to open the mine to tourists, look for the information panels featuring reproductions of Edo period (1603–1867) drawings used to describe the functions of the mine to government officials.

13.Sakaneguchi Checkpoint Site

When the central government in Edo (present-day Tokyo) assumed direct control of Iwami Ginzan in the early 1600s, a fence was built around the silver mine and checkpoints established at all exits to regulate the flow of people and goods into and out of the mining area. The guards at these checkpoints were tasked with ensuring that taxes were paid on goods entering the mine, that silver destined for the government’s coffers was not smuggled out, and that only people authorized to work and/or live in the fenced-off zone entered it.

There were 10 checkpoints around the central mining area and many more throughout the Ginzan Goryo, the area under direct government control, which encompassed some 150 nearby villages. Sakaneguchi was the last checkpoint on the road to the port of Yunotsu, the main conduit for transport of materials to and from the mine, and therefore particularly important. No trace remains of the checkpoint building, which was where the nearest house now stands, but the road to Yunotsu is still intact. From Sakaneguchi, it leads over a mountain pass and through the village of Nishita to the port, five hours away on foot.

14.Tochihatadani Settlement Site

The Tochihatadani valley is the site of one of the oldest mining communities at Iwami Ginzan. Dating back to the mid-1500s, the settlement was expanded as the silver mine flourished in the late 1500s and early 1600s and remained inhabited at least into the middle of the Edo period (1603–1867). Miners and their families lived in houses built on flattened and terraced ground, and they likely worshiped at the several Buddhist temples that appear in Edo-period descriptions of Tochihatadani. While none of the homes or religious sites remain, some of the stone retaining walls built to fortify the terraces can still be seen. The openings of several mining tunnels are also visible along the hillside.

Besides having been settled early, Tochihatadani is notable for having been one of the more international communities at Iwami Ginzan. The Korean and Chinese residents who figure in records concerning the site may have been technical advisors, who helped relay knowledge of advanced ore processing techniques to Japan. Among these techniques was the haifuki (cupellation) method of refining silver, invented on the Korean peninsula and introduced to Iwami Ginzan in 1533. This year is considered a turning point in the history of the mine, because the haifuki method made it possible to produce large quantities of the high-purity silver that Iwami Ginzan became renowned for and that contributed to the world economy from the mid-1500s onward.

15.Sahimeyama Shrine

Sahimeyama Shrine stands on a hill about 200 meters from the entrance to the Ryugenji mining tunnel, one of the central sights at Iwami Ginzan. When the silver mine flourished in the late sixteenth and early seventeenth centuries, this site was both the spiritual and physical center of a large mining settlement that spread out across the entire hillside around the shrine.

The sanctuary enshrines Kanayamahiko no Mikoto, the Shinto god of mining, and is built directly above what was once one of the most abundant silver veins in the area. Miners and their families, who said their daily prayers at the shrine, lived in houses built on artificially flattened and terraced ground in the vicinity. While none of the houses remain, many of the stone walls built to fortify the terraced ground can still be seen.

Sahimeyama Shrine has remained a key religious institution throughout the history of Iwami Ginzan; its current buildings date to 1819 and include an unusually large worship hall (haiden). The large worship hall was designed to accommodate performances of kagura dances to honor Shinto deities that remain a core part of folk traditions in the Iwami region.

16.Kobuyamadani Settlement Site

The Kobuyamadani valley is located about 200 meters from the entrance to the Ryugenji mining tunnel, one of the central sights at Iwami Ginzan. When the silver mine flourished in the late sixteenth and early seventeenth centuries, a large mining settlement was built across the entire hillside. Houses and facilities for processing silver ore were constructed on flattened and terraced ground, at a convenient distance from the many mining tunnels dug into the rock. The Kobuyamadani settlement proved enduring: it was expanded gradually over the centuries and remained populated until the Meiji era (1868–1912). This was partially thanks to its relatively convenient location near the foot of Mt. Sennoyama, around which the silver mine was located. The low-lying setting, however, was also a curse: Kobuyamadani was often hit by floods, some of which caused severe damage.

In the upper part of the valley is the Shinyokoai mining tunnel, which was developed in the middle of the Edo period (1603–1867) and is a testament to the ingenuity of Kobuyamadani’s miners. To reach the vertical silver veins, the tunnel was dug into the mountainside horizontally and at a slight upward angle so that groundwater released by mining would flow out. Traditional mining tunnels were dug at a steep downward angle parallel to one or several silver veins, but they would sooner or later fill up with water. In addition to developing this innovative type of tunnel, the Kobuyamadani miners took up copper mining when the silver deposits in the area were depleted. These efforts were continued in the Meiji era, when the Fujita-gumi corporation acquired rights to Iwami Ginzan and built modern ore dressing and refining facilities in the valley. Those functions were moved to the nearby Kojidani area at the turn of the twentieth century, and Kobuyamadani fell silent after some 350 years of mining.

17.Ishigane Settlement Site

Near the summit of Mt. Sennoyama, around which the Iwami Ginzan silver mine grew from the mid-1500s onward, is a relatively flat, terrace-like expanse covered with low grass. This is Ishigane, where a major mining community flourished in the early 1600s. Populated during the silver mine’s greatest period of prosperity, the settlement centered on a road that led down the hillside into the Hondani valley, another important mining hub. This road, now reconstructed, was about 2 meters wide and lined with buildings on both sides.

As evidenced by the remains of refining pits, crushed ore, and other items excavated here, miners and their families both lived and worked in these houses, dressing, smelting, and refining silver ore mined in nearby tunnels. The homes had clay walls for fire safety, and fresh water—a prerequisite for life in a place this isolated—was carried from a nearby well.

The stone foundations of one miner’s home and workshop have been partially reconstructed near the middle of the former settlement, in front of a narrow mining tunnel. The excavation of this site in the 1990s turned up one of the most significant archaeological finds in the modern history of Iwami Ginzan: a sixteenth-century iron pot that was used to refine silver using the haifuki (cupellation) method. Historical documents suggest that this technique, the key to producing high-quality silver at the time, was introduced to Japan from the Korean peninsula in 1533, but the iron pot discovered at Ishigane was the first physical evidence tying the haifuki method to Iwami Ginzan.

The excavation at Ishigane also helped shed light on the structure of mining communities at Iwami Ginzan. It appears that mining and processing silver was a job that families often performed together as units. One poignant find at the site was a lock of a woman’s hair tied to form an amulet of sorts, perhaps a lucky charm given by a wife to her husband to keep him safe down in the mines.

18.Ishigane Senjojiki Settlement Site

In the early 1600s, the relatively flat, terrace-like expanse near the summit of Mt. Sennoyama hosted several mining settlements, including Ishigane, Ishigane Fujita, and Ishigane Senjojiki. Populated during the Iwami Ginzan silver mine’s greatest period of prosperity, these settlements centered on a road that led down the hillside into the Hondani valley, another important mining hub. This road, now reconstructed, was about 2 meters wide and lined with buildings on both sides. The remains of refining pits, leftover ore, and other archaeological evidence discovered in the 1990s on the southeast side of the terrace, in what was once Ishigane Senjojiki, proved that miners and their families both lived and worked here, dressing, smelting, and refining silver ore mined in nearby tunnels. Their homes, which doubled as workshops, had clay walls for fire safety, and fresh water—a prerequisite for life in a place this isolated—was carried from a nearby well. None of the structures remain of what was once a large community (as suggested by the name Senjojiki, or “a thousand tatami mats”), but the openings of several mining tunnels can be seen along the hillside. The tunnels were dug using only chisels and hammers, and the time and effort required resulted in their being just wide enough for a miner to squeeze through.

19.Kamaya Mine Tunnel and Surroundings

The Kamaya tunnel is the source of one of the greatest success stories in the history of Iwami Ginzan. It was dug in 1602 by a prospector named Yasuhara Denbei, who soon discovered an abundant silver vein within. During the following year, Kamaya produced a remarkable 13.5 tons of silver for the shogunate, the central government in Edo (present-day Tokyo), which had assumed direct control of the mine a few years earlier. This contribution was so great that Yasuhara was granted an audience with shogun Tokugawa Ieyasu (1543–1616) and an honorary title, and he was presented with an ornate dofuku jacket and fan. The jacket was donated to Seisuiji Temple, where Yasuhara is said to have prayed before his discovery, and is now designated an Important Cultural Property. A reproduction of the jacket is on display at the Iwami Ginzan World Heritage Center.

Several mining sites from the early 1600s have been discovered in the vicinity of the Kamaya tunnel. In some, miners appear to have dug directly into the hillside rather than use tunnels, because the silver veins in this area were often very close to the surface.

Cliffs were also cut into to flatten the ground and make room for buildings. Nearby, pits were dug into the rock to collect rainwater, which was needed to wash the ore so that silver-containing bits could be collected effectively. These remains, along with byproducts of the silver-refining process found here, indicate that both sides of the valley that centers on the Kamaya tunnel were mined heavily from the time of Yasuhara Denbei through to the Meiji era (1868–1912), when the last shafts in the area were dug.

20.Okubo Mine Tunnel

Okubo is the largest tunnel system at Iwami Ginzan and one of the two main mining tunnels open to visitors on a regular basis.

It is one of the most thoroughly excavated parts of the silver mine, having been mined from the late 1500s until the Meiji era (1868–1912) and enlarged repeatedly over the centuries. Distinguished by its high entrance, the tunnel bears the name of Okubo Nagayasu (1545–1613), the first magistrate appointed by the Tokugawa government to oversee Iwami Ginzan.

Several smaller shafts branch out from the main tunnel, which is as high as 5 meters in places. These were dug to follow the veins of silver, traces of which are still visible here and there along the walls. There are also vertical shafts, some for ventilation and others that were used to route groundwater outside. The walls of the main tunnel are smooth where they were shaped by chisels and hammers. The tunnel was widened in the Meiji era to accommodate carts, so other parts of the walls bear marks of rough excavation techniques, including the dynamite used to widen the passage. Some cart rail crossties from this time are still visible on the ground.

Guided tours of the Okubo tunnels are given on weekends and public holidays from April to November. In winter the tunnels become the domain of hibernating bats, which can be spotted flying around inside year-round.

21.Hondani Settlement Site

Although it is now heavily forested and serene, Hondani (“main valley”) was one of the most important mining centers at Iwami Ginzan from the latter half of the 1500s to the late 1700s. A sizable settlement extended through the valley, where houses that also served as workshops for processing silver were built on flattened and terraced ground.

Near the entrance to the valley is the Okubo tunnel, the largest system of mining tunnels and shafts at Iwami Ginzan, and further down is the 800-meter-long Kinsei tunnel, dug to release groundwater from the Okubo system. Uphill along the valley, both sides are dotted with narrow tunnels and sites where miners appear to have dug directly into the cliff, because the silver veins in this area were often very close to the surface. Most of these sites have been reclaimed by nature and are difficult to spot, but some have been excavated around the Kamaya tunnel, which, in the early 1600s, sparked a dramatic increase in the mine’s silver output. Some of the stone walls built to fortify the terraced ground can also be seen here. Even further up is the entrance to the Honmabu (“main tunnel”), dug above one of the most abundant silver veins in the area. From here, the valley narrows as it continues up toward the summit of Mt. Sennoyama and Ishigane, the site of another major seventeenth-century settlement. Visitors should note that the path from Honmabu to Ishigane is not well maintained and can be difficult to traverse.

22.Hondaniguchi Checkpoint Site

Hondaniguchi oversaw the entrance to Hondani (“main valley”), one of the key mining centers at Iwami Ginzan until the late 1700s. Some of the mine’s most productive tunnels and shafts were in Hondani, and a significant number of miners and their families lived in this area. This made the twin checkpoints of Hondaniguchi and nearby Mizuochiguchi key nodes in the policing of the mine. Nothing remains of the checkpoint building, but a small mound by the road indicates its location.

23.Kojidani Area and Eikyu Refinery Site

Now all but entirely reclaimed by nature, the Kojidani valley was a hub of intense mining activity only a century ago. This activity centered on the Eikyu mining tunnel, which was originally dug between 1693 and 1787 as part of a system of tunnels and shafts that routed groundwater from several mining sites further uphill into the Kojidani River at the bottom of the valley. The Eikyu and the rest of the mine had been dormant for decades when the Osaka-based Fujita-gumi corporation acquired rights to Iwami Ginzan in 1886. Fujita-gumi invested heavily, introducing cutting-edge mining equipment and methods, including using dynamite to expand existing tunnels and shafts and extract large amounts of ore. The Eikyu tunnel was among those targeted, and in 1899 it yielded a significant discovery in the form of the abundant Uchinakase copper vein.

This breakthrough led Fujita-gumi to open a new refinery in Kojidani in 1902. Employing the latest technology, the facility processed copper into ingots that were sent to Kosaka in northern Akita Prefecture to be refined further. The entire mountainside was cleared, and various structures, including an ore dressing plant and a coal-fired power plant, were built around the refinery, which at its height employed hundreds of people. The Eikyu tunnel was gradually expanded until it reached a depth of more than 300 meters. Fujita-gumi’s operations in Kojidani continued until 1923, when years of low copper prices on the world market finally took their toll and the facilities were closed for good.

Very little remains of the Eikyu Refinery in the forested valley. The main structure was swept away by a landslide in 1943, and the entrance to the Eikyu tunnel was buried by a dam completed in the late 1960s. Brick and concrete foundations, including walls built to fortify the terraced ground underneath the ore dressing plant, can still be seen if you know where to look, and a monument to mine workers who died on the job, erected in 1913, stands in the inner part of the valley.

Sennoyama: The Silver Volcano

It is no exaggeration to say that Iwami Ginzan became one of the world’s most productive silver mines thanks to the distinctive geological features of Mt. Sennoyama, the ancient volcano around which the mine grew from the mid-1500s onward. The mountain began to take shape some 1.5 million years ago, when a volcanic eruption caused a pileup of pyroclastic material such as extremely hot ash and chunks of partially solidified lava around the crater. The newly formed peak was notably brittle, like a giant pile of sand.

Volcanic activity continued underneath the mountain, with magma heating groundwater from below and turning it into hydrothermal water, a fluid that has a temperature of more than 200°C but does not boil away due to the high-pressure conditions deep underground. The hydrothermal water’s heat released elements including silver and copper from the nearby rock and magma. This metal-containing fluid then seeped upward through cracks in the bedrock, penetrating the porous Mt. Sennoyama and transporting silver throughout the mountain. As the liquid cooled and solidified due to the change in temperature and pressure, countless silver veins were left in the coarse rock.

When prospectors in the 1500s started mining at Mt. Sennoyama, they noticed that several of the silver veins they discovered were located close to the surface—a result of the hydrothermal water’s extensive flow through the brittle mountain. These characteristics meant that many of the veins were both heavily laden and relatively easy to reach even with chisels and hammers, which miners used to dig into the mountainsides before the age of explosives.

Okubo Mine Tunnel: A Gateway to the Past

Mining in the Okubo tunnels, the largest tunnel system at Iwami Ginzan, began in the late 1500s and continued until 1896. Many traces of this 300-year history remain intact within the tunnels thanks to the distinctive environment inside the mountain.

The Okubo tunnels were initially dug using chisels and hammers, the marks of which can still be made out on the smooth parts of the main tunnel’s walls. Other sections bear scars of the rougher excavation techniques used in the late 1800s, when the tunnel was widened to accommodate carts. Although the cart rails were removed after the end of mining in 1896, some rail crossties from this time remain in place. Dents in the ground at regular intervals, where more crossties used to lie, are also visible.

One of the crossties in the tunnel still has a pair of rail spikes that were left in the wood after the rails were detached. These nineteenth-century “dog spikes”—named after the shape of their top part, which looks like a dog’s head—are the only nails of their kind in Japan known to have survived intact inside a mining tunnel for well over a hundred years.

The dog spikes were spared from rust and the crossties from decay because of the tunnels’ wet environment. Water seeps ceaselessly through the surrounding brittle rock, dousing the tunnel floor and preventing the rails’ remains from interacting with the air. Equally importantly, the water is free of heavy metals (it is even pure enough for drinking), as it has been throughout the history of Iwami Ginzan.

The Okubo system can be explored on guided tours of the tunnels, which are given on Fridays, weekends, and public holidays from March to November. In the months before Christmas, the tunnels are used by a local baker to age stollen, a type of sweet yeast bread baked with fruits and nuts. This traditional German holiday delicacy has in recent years become a local culinary attraction.