The History of Tomogashima and Yura Fortress
Tomogashima is the collective name for a group of islands located off the coast of Kada in Wakayama City, Wakayama Prefecture. The group consists of Okinoshima, Jinoshima, Torajima, and Kamijima, and the islands are part of Setonaikai National Park.
Although Tomogashima is now a peaceful natural area, it once served as an important military position protecting Osaka Bay. During the Meiji period, as Japan rapidly modernized, the government recognized the need to defend the country against foreign naval forces. A large-scale fortress system was therefore constructed around the Kitan Strait, the entrance to Osaka Bay.
The central defense system was known as Yura Fortress. Its headquarters were located in the Yura area of Awaji Island, which gave the fortress its name. Gun batteries and defensive facilities were strategically positioned around Yura on Awaji Island as well as Tomogashima, Kada, and Miyama on the Wakayama side. It became one of Japan’s important coastal defense systems.
On Tomogashima, five batteries, numbered from the First to the Fifth Battery, were constructed and developed between 1890 and 1904. Among them, the Third Battery was built as the largest and most important main artillery position on the islands.
Features of the Tomogashima Third Battery Ruins
One of Tomogashima’s Largest Main Batteries
The Third Battery was the most important of the artillery positions constructed on Tomogashima. It was designed to engage enemy warships passing through the Kitan Strait and was equipped as a powerful coastal artillery battery.
One of its most distinctive features is the large, bowl-shaped gun emplacement. Unlike many conventional batteries, the position was designed with an almost 360-degree field of fire, allowing it to respond to enemy ships approaching from different directions.
The surrounding complex also included facilities essential to the operation of the fortress, such as a power station, guard quarters, and ammunition storage areas. These remains provide valuable insight into Japan’s military technology and coastal defense strategies during the country’s modernization in the Meiji period.
Underground Ammunition Storage and Hidden Facilities
One of the most fascinating aspects of the Third Battery Ruins is the opportunity to explore parts of the underground complex.
Underground passages extend beneath the gun emplacements, connecting facilities such as ammunition magazines and shell-lifting equipment used to transport artillery shells from underground storage areas to the guns above.
Visitors can still descend into some of these underground areas and see spaces surrounded by thick walls as well as traces of the original equipment. The cool, dark atmosphere and brick-built chambers provide a vivid impression of the site’s former role as a military installation.
Rare Remains of a Shell-Lifting Mechanism
The Third Battery contains a particularly interesting piece of surviving military equipment: a shell-lifting mechanism, a feature rarely preserved at former Japanese fortress sites.
The mechanism was designed to raise artillery shells from the underground magazines to the gun emplacements above, allowing the artillery crews to operate more efficiently. Parts of the original pulley system remain, offering visitors a glimpse into the practical engineering behind the fortress.
“Iroha” Markings Around the Gun Emplacements
If you look carefully around the gun emplacements, you may find the Japanese characters “Iroha” marked near areas where ammunition was placed.
These markings are thought to have been used to identify specific ammunition positions. Small details such as these help visitors imagine how the battery was organized and operated more than a century ago.
A Mysterious Landscape Where Nature and Ruins Meet
The appeal of the Third Battery Ruins goes far beyond their historical importance.
Over the course of more than a century, the brick buildings and stone walls have gradually been reclaimed by nature. Moss and vegetation cover parts of the structures, while dense forest surrounds the former military facilities. The combination of man-made fortifications and vigorous natural growth creates a landscape unlike almost anywhere else in Japan.
The sight of plants growing over the circular gun emplacements is particularly atmospheric. Visitors often describe the scenery as resembling an anime setting or another world, making the ruins an especially popular destination for photographers.
Because of their striking appearance, the ruins have also been used as a location for photography and various media productions. Their combination of weathered architecture, dense forest, and underground passages makes them an exceptional place for capturing atmospheric images.
The Tomogashima Third Battery Museum: An “Audio Museum”
A New Artistic Experience Within a Historic Fortress
In October 2019, the Third Battery Ruins gained a new dimension as a cultural and artistic attraction with the opening of the Tomogashima Third Battery Museum.
Rather than functioning like a conventional museum filled with display cases, the museum uses the historic battery itself as the setting for an immersive experience involving sound, light, and the surrounding darkness.
Visitors enter the quiet underground spaces, experience artistic lighting in the darkness, and listen carefully to the sounds around them. This creates a different way of experiencing a historic site, allowing visitors to engage with the ruins through more than simply looking at them.
An Immersive Experience with an Audio AR App
The Third Battery Museum can also be experienced through the Tomogashima audio AR tourism app.
By adding sounds and storytelling to the historic fortress environment, the experience creates an unusual connection between the past and the present. The former military site takes on a new role as a place for art, tourism, and cultural interpretation.
This transformation is one of the most fascinating aspects of the Third Battery Ruins: a place originally designed for warfare has become a destination where visitors can experience history, nature, and contemporary artistic expression together.
Tips for Visiting the Third Battery Ruins
The Third Battery Ruins are relatively well preserved and many areas can be explored, but visitors should remember that this is a historic structure rather than a modern tourist facility. Care should be taken when walking through the site.
Some underground areas are very dark, and parts of the ground and stairs may be uneven. Although a smartphone flashlight can provide some illumination, bringing a flashlight is strongly recommended for a safer and more comfortable visit.
Because reaching and exploring the ruins involves walking along forest trails, comfortable walking shoes and practical clothing are also recommended. Visitors should take extra care when conditions are wet or slippery.
Other Historic Sites on Tomogashima
First Battery Ruins
The First Battery was constructed near the cliffs at the western end of Tomogashima to attack ships passing through the Kitan Strait. Nearby stands the Tomogashima Lighthouse, built in the early Meiji period. Visiting the area offers an opportunity to experience both the history of Japan’s coastal defenses and the development of modern lighthouse technology.
Second Battery Ruins
The Second Battery was built as a defensive artillery position designed to attack enemy ships from the side. Some of the structure has deteriorated due to exposure to waves and weather, and the area is currently closed to visitors. Even from outside the restricted area, however, the remaining structures convey the impressive scale of the former fortress.
Fourth and Fifth Battery Ruins
The Fourth Battery served a supporting role for the Third Battery, while the Fifth Battery was constructed to protect important facilities on the island. Stone walls and other remains can still be found among the forest, providing clues to the defensive network that once covered Tomogashima.
Nature and Legends of Tomogashima
Tomogashima is not only a destination for military history. The islands are also known for their rich natural environment and ancient religious traditions.
Broad-leaved evergreen forests cover much of the islands, which are home to wildlife including deer, squirrels, and peafowl. Around Fukaja Pond, visitors can also encounter wetland plants of ecological importance, making the islands attractive for nature lovers as well as history enthusiasts.
Tomogashima has also long been associated with Shugendo, a Japanese mountain ascetic tradition. Legends connected with En no Gyoja, a legendary ascetic traditionally regarded as an important figure in the origins of Shugendo, have been passed down through generations. Torajima contains a traditional ascetic training site, adding another layer of history and spirituality to the islands.
Conclusion: Where History, Nature, and Art Come Together
The Tomogashima Third Battery Ruins are a remarkable destination where Meiji-era military technology, the history of warfare, abundant nature, and contemporary art come together.
Weathered red-brick ruins, underground ammunition magazines, gun emplacements surrounded by forest, and an artistic museum using sound and light all contribute to an experience that goes far beyond an ordinary sightseeing visit.
Located approximately 20 minutes by boat from Kada Port, Tomogashima feels surprisingly distant from everyday life. Its combination of mysterious ruins and beautiful natural scenery creates the atmosphere of another world.
For travelers interested in Japanese history, military heritage, abandoned architecture, photography, nature, or unique cultural experiences, the Third Battery Ruins and the wider Tomogashima islands are well worth adding to a Wakayama itinerary.