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Delving into the Depths of Japan’s Mysterious Tonkararin Tunnels

Delving into the Depths of Japan’s Mysterious Tonkararin Tunnels


Within the sloping mountains of Japan lies a mysterious ruined tunnel structure known as the Tonkararin Tunnels. This ancient ruin likely dates to the 5th or 6th century of Imperial Japan, although its true age remains unknown. Archaeologists, scientists, and locals constantly argue about why this tunnel system was built. Some academics theorize it was it built for a Shinto ritual connected to the nearby Eta Funayama tomb. Others state that it is an intricate agricultural or travel route, created by Korean immigrants . There are even adherents to the theory that it is the hideaway of the ancient Goddess Amaterasu. To understand why this ancient ruin exists, we must delve into the depths of ancient Japanese history to try and unravel the past.

Putting the Tunnels in Context: Yayoi, Kofun and Present

This ancient series of tunnels was discovered by archaeologists in the 18th century and re-examined in the 1970s. It measures approximately 1,460 feet (445 meters) in length and varies in width and height. At its tallest the tunnel reaches 13 feet high (4 meters) with areas narrowing into crawl-like spaces. These unique measurements have prompted archaeologists to theorize that these tunnels were created for or by water fissures that would lead to the Kofun tombs nearby. At first glance this 1970s theory appears to be logical. The tunnel system runs along the slope of a mountain, and one can walk the distance to the Kofun tombs within five or ten minutes.

A natural fissure could have created uniquely shaped waterways, which would be easy to use for ancient people. However, on closer inspection, archaeologists have tossed this theory aside. A quick google image search illustrates why. The tunnels have a clean human-made design. The rectangular entrance leads to a staircase sloping inwards to the tunnels. The moss covered stone likely took great strength and effort to carve into. While some fissures of the tunnels could have been caused by water and wind erosion, the entrance and stairs were clearly carved by hand with great care. This megalithic ruin winds through darkness in varying widths and heights. Clearly these tunnels have lasted thousands of years. But when exactly were they created, and by whom?

The tunnels have clearly been created by humans, but when and by whom? One segment of the Tonkararin Tunnels in Japan. (Ozizo / CC BY-SA 3.0)

The tunnels have clearly been created by humans, but when and by whom? One segment of the Tonkararin Tunnels in Japan. (Ozizo / CC BY-SA 3.0 )

When Were These Mysterious Tunnels Created?

The Tonkararin Tunnel is located in Nagomi, a town in the Kumamoto Prefecture of Northern Kyushu of Japan. This countryside area has a rich and long history, filled with the rising a falling of varying civilizations. Many researchers associate this tunnel with the Eta Funayama tomb, which likely dates to the Kofun period. However, could this ancient site have been created before the royal tombs? To find out, we need to examine the Yayoi Period , the century that ushered in Kofun traditions.

The Yayoi period took place between 300 BC and 300 AD. This period brought many changes to Japan, likely from Korea, including wet- rice cultivation. The people of this civilization lived in thatched houses and semi-subterranean homes. This era brought dolmens to the forefront of funerary practices. These were table-shaped burial motifs, that changed over time. When dolmens reached Northern Kyushu, they merged with burial pits and accommodated burial goods like pots, jars, and tubular beads. The Yayoi culture brought new changes to Japan, and potentially influenced the Tonkararin Tunnel. Considering this culture utilized moats for many purposes, the fissure within this mountain could have inspired the residents.

Built during the Kofun Period, the Daisenryo Kofun, the largest kofun in Japan, is a spectacular example of a megalithic keyhole tomb in Sakai, Japan. (Claude Jin / Adobe Stock)

Built during the Kofun Period, the Daisenryo Kofun, the largest kofun in Japan, is a spectacular example of a megalithic keyhole tomb in Sakai, Japan. ( Claude Jin / Adobe Stock)

Burial Mounds and Ornate Tombs of the Kofun Period

Soon after the Yayoi period, the Kofun Period began at 300 AD. This era was appropriately named for the Kofun mounds across Japan. These burial mounds contained chambers and tombs for the members of the ruling class. These tombs were shaped similarly to keyholes, becoming more complex with time. The third, fourth and fifth centuries generally contained unadorned and simple tombs. However, the fourth and fifth century did see more burial mounds, signifying the unification of the power of the ruling class. Towards the end of the 5th century, haniwa or clay cylinders were introduced into the burial mounds. The Sueki pottery ware present in these tombs are eerily close to present-day modern porcelain and contained blue-grey pigments.

The 6th century Kofun period was reminiscent of the great tombs of New Kingdom of Egypt. Kofun burial mounds contained painted walls, large sarcophagi, burial goods of bronze mirrors, swords, horse trappings. The gloriously beautiful tombs contained ornate sculptures, personal ornaments, and beautiful clay vessels. 

The Kofun period saw both imperialism and Shinto beliefs. The unification of statehood and religion led to connection amongst different villages in Japan. One belief that unified the archipelago of Japan was the folklore of Amaterasu, sun and solar Goddess. This deity is supposedly the ancestor of the emperors of Japan. A common theme in this folklore is the goddess hiding inside a rock cave, which could have great significance to the Tonkararin tunnels. 

Connecting the Tonkararin Tunnels to the Yayoi-Kofun Periods

Why do the Yayoi and Kofun periods matter? The answer is simple. They are the likely architects of these mysterious tunnels. The Yayoi residents probably attempted to create a system for agricultural use. These tunnels could have created a short cut to other fields or provided water to their rice farms. Unfortunately, there is no archaeological evidence to support this theory.

So, what about the Kofun period? During the Kofun period, key-shaped burial mounds began sprouting across Japan. These shared the dolmen structure of the Yayoi period, but added more details. The Tonkararin Tunnel is less than a ten-minute walk to the Eta Funayama burial mound. Many archaeologists have theorized this tunnel system is in fact connected both by the location and with the spirit of this mound. They believe it is part of a key shamanistic ritual . At the time, Shinto was the nation’s religion, a religion that translates to “The Way of the Gods”.

A narrow section of the Tonkararin Tunnels, which is covered with stones. (Ozizo / CC BY-SA 3.0)

A narrow section of the Tonkararin Tunnels, which is covered with stones. (Ozizo / CC BY-SA 3.0 )

The Influence of Shinto Religious Practice

Archaeological evidence of the early Shinto religious practice illustrates a respect for agriculture, water supplies and seafaring. Rituals included mirrors and swords, two items that could help spiritual forces. The mirror is revered as a sacred object representing the sun goddess Amaterasu. To complete the Shinto rituals of mirrors one must make a pilgrimage to the local shrine. Upon arrival one must bow at the mirror hung in the shrine entrance. Next, the worshipper bows in front of the mirror and views their own reflection. This moment is meant to reflect the inner self and purify the worshipper. Next, one must walk to the shrine’s inner sanctum, and bow in front of the mirror placed there. This set of mirrors is the body of Amaterasu in her earthly form.

According to Bernard, Shinto religion and ecology walk hand in hand. Shinto ritual practices rely on unique landscapes, which explains why many of the shrines are located on mountain sides. The natural environment has a starring role in Shinto beliefs, but remains separate from Buddhism. The key differences between both religions can be found in the deities worshipped.

Shinto during the Kofun period illustrates the rise of the state. Royals utilized village shrines to help solidify their power across Japan’s archipelago. The boundaries between nature, human and deities are blurred during Shinto ceremonies. Locations of shrines hold great importance and help blur these lines. Folklore claims that a Shinto shrine which is close to a village is focused on agriculture and will likely have worship of the season deities. These deities will bring a stronger harvest. However, if a shrine is located between nature and human beings, it is meant to interconnect them. This shrine will help ward of chaos for the worshippers and bring nature to their social environment. It is important to note that these shrines are usually found in mountains, rivers and forested groves. This shrine located in these areas exudes a sacredness and represents the communities nearby.  

The Eta Funayama burial mound in Nagomi is very near to the Tonkararin Tunnel. (Public domain)

The Eta Funayama burial mound in Nagomi is very near to the Tonkararin Tunnel. ( Public domain )

Treasures of the Eta Funayama Burial Mound

The Tonkararin tunnel is located a short distance from the Eta Funayama burial mound. Its proximity has caused archaeologists to associate the tunnel with the mound. The mound was first excavated in 1873, an impressive feat considering the tumulus is a sixty-two-meter-long keyhole-shaped tomb. Within this tomb, archaeologists found a dolmen, or a sarcophagus-style stone. This had a side opening within the round keyhole portion of the mound. Upon opening this mysterious stone slab, archaeologists would find treasures adding to the mystery of this mountain side tunnel.

This ancient site contained intricate bronze mirrors. One such mirror was decorated with images of deities and beasts of unknown origin. It is likely this mirror had great meaning for royalty. As the archaeologists explored deeper and deeper into the great tomb, more mirrors were uncovered. Each designed with different beasts and deities. A unique mirror contained only four beasts and the bronze still shines today in the National Tokyo Museum. 

Along with the reflective surfaces found, tubular shaped beads have been discovered. These beads varied in color, stones, and size. These are reminiscent of the Yayoi culture and Korean burial mounds. Jadeite magatama jewels were uncovered along with glass and Talc comma-shaped jewels. These items look strikingly similar to post-modern art.

Jewelry, beads, and mirrors were not the only items found within this monument. Swords were uncovered, double-edge blades, iron swords, sword accessories and even armor. Clearly, warriors were buried here, or at the very least, someone was prepared for battle.

Mirror discovered in the Eta Funayama tomb. The mirror is revered as a sacred object representing the sun goddess Amaterasu. In Shinto religious practice, looking in a mirror is meant to reflect the inner self and purify the worshipper. (Daderot / CC0)

Mirror discovered in the Eta Funayama tomb. The mirror is revered as a sacred object representing the sun goddess Amaterasu. In Shinto religious practice, looking in a mirror is meant to reflect the inner self and purify the worshipper. (Daderot / CC0)

Royalty in the Mountains?

Perhaps the most famous discovery of the Eta Funayama tumulus was discovered by local residents. The story of how this was found is lost in the past. However, what remains is the discovery of a golden crown and gold gilt sword with an inscription, as well as other royal items. Gilt-bronze headdresses were discovered, fit for a queen, while one gilt-bronze crown was discovered. The treasures that gleamed in this dark tomb did not end here. Golden earrings, rings, and plates all shimmered with any ounce of light.

The list of artifacts found is a long one, and it gives a clearer picture of life during the Kofun period. The use of bronze, iron, silver and gold show great craftsmanship. The ring-shaped stirrups, helmet of armor and short armor paint of picture of a war ready society. The iron arrowheads found along with swords show the importance of the military and imply the close association of power and royals. The gorget found within this treasure trove suggests royalty fought in battles as well. This item was similar to armor, but it covered the neck and provided protection for the face.

Along with these military items, a triple ring bell was located. This unique item is likely a religious bell, important for individualistic rituals. It is important to note that bells were also used for farming animals during the Yayoi period. During the Yayoi period, various sizes of bells were buried within the hill side. This was to create fertile land for a fruitful harvest.

So why was this bell buried within the Eta Funayama tumulus? Military items and jewels are to be expected in most great tombs. But a three-ringed bell associated with a farmer? Perhaps the answer still lies within the mountainside itself?

The Tokyo museum holds most of these artifacts, however many have been lost to the ages. There are several colorful rumors of artifacts being spread across the world and sold into private collections. Much like the treasures of Egypt, Pompeii, and China have gone missing over time. One must ask, could one of these missing artifacts hold the answer to the Tonkarin Tunnels? Was there a golden laced manuscript explaining its purpose? Or are there simply no true answers to this mystery? Perhaps the key to unlocking these answers could lie in taking a step back and viewing the mountainside tunnel as a shrine.

The mysterious tunnel system has clearly existed for thousands of years. Could the Goddess Amarerasu herself have disappeared inside its winding paths? (Explore Kumamoto)

The mysterious tunnel system has clearly existed for thousands of years. Could the Goddess Amarerasu herself have disappeared inside its winding paths? ( Explore Kumamoto )

Are the Tonkararin Tunnels a Shrine?

Thanks to a cursory discussion of the history and religion of Kyushu, it seems likely that Tonkararin Tunnel could be a shrine. First, it is located in close proximity to its community, burial mound and in the slope of a mountain. This mysterious tunnel has clearly existed for thousands of years and could be the prototype of Shinto shrines . Its carefully carved stone shows great respect for the surrounding nature. The artifacts buried inside the Eta Funayama tomb include ritualistic items associated with the Shinto religion. Perhaps the Goddess Amaterasu herself disappeared into this rock laden slope and to hide from brother. Either way, the Tonkararin tunnel remains a sacred and mysterious ruin, which serves to allow our historic imagination run wild.

Top image: Archaeologists, scientists, and locals constantly argue about why the Tonkararin Tunnels were built. Source: Pakon / Adobe Stock

By Elizabeth Moore


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Pete Wagner's picture

When you see the term, ‘funerary practices’, be very skeptical.  Ask yourself what else could it have been.  Could it have been mass genocide in some regional or global calamity?  Were many killed in a single event, or does the evidence suggest normal morality rate for the population (i.e., about 1 percent per year)? 

The fact, however, that ancient civilized cultures burned dead bodies is well-established in the ancient texts.  The latin root word for funeral is torch.  The only other well-established ancient method of disposing bodies, typical of more primitive societies, was laying the body out for the scavengers, e.g., vultures and hyenas.  The ceremonial burial of dead bodies, as a cultural practice, has its mysterious origins with Jews and Rome.  Makes you wonder why they stopped burning bodies.

Nobody gets paid to tell the truth.

Elizabeth Moore's picture


Elizabeth Moore is an archaeologist, writer, and traveler. Growing up in Southern California with an Australian father, Los Angeles mother and Eastern European grandparents instilled a sense of wanderlust within her. While much of her close-knit family resides in other... Read More

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