Shizu-no-Iwaya Cave is a spectacular sea cave located along the coast of Uozu in Shizuma Town, Oda City, Shimane Prefecture. Situated west of the mouth of the Shizuma River, the cave was carved over countless years by the powerful waves of the Sea of Japan.
The cave is approximately 45 meters deep, 13–15 meters high, and 30 meters wide. Its large chamber has two openings facing the sea, creating an impressive natural landscape.
For centuries, Shizu-no-Iwaya has been regarded as a sacred and mysterious place. It is closely associated not only with the natural history of the region, but also with Japanese mythology and classical literature. Although visitors are currently prohibited from entering the cave because of the risk of rockfalls, its historical and cultural significance continues to attract visitors.
Shizu-no-Iwaya is particularly famous for its connection with the Man’yoshu, Japan’s oldest surviving collection of poetry. In Volume 3, the poet Oshi no Suguri Mahito composed a poem referring to a place called Shizu no Iwaya.
The poem asks how many ages have passed since the deities Okuninushi-no-Mikoto and Sukunahikona-no-Mikoto stayed at this rocky chamber. One of the locations traditionally identified with the Shizu no Iwaya mentioned in the poem is today’s Shizu-no-Iwaya Cave.
In Izumo mythology, Okuninushi-no-Mikoto and Sukunahikona-no-Mikoto are important deities associated with the development and ordering of the land. According to local tradition, the two gods temporarily stayed at this cave while carrying out their work of kunizukuri, or the creation and development of the land.
The rocks forming Shizu-no-Iwaya date back approximately 15 million years. They consist mainly of tuff and volcanic breccia created when volcanic ash and rock produced by ancient volcanic activity accumulated on the seabed.
During the period when the Japanese archipelago was undergoing major geological changes, complex faults and rock formations developed within these layers. Over a much longer period, waves from the Sea of Japan gradually eroded weaker sections of the rock, eventually creating the enormous sea cave visible today.
The cave’s rugged rock surfaces preserve evidence of these geological processes. Even when viewed from outside, the immense scale of the formation offers a vivid sense of the Earth’s long history.
Inside, the cave is naturally dark, while light from the sea filters through the openings and illuminates the rock walls. This creates an almost otherworldly atmosphere and helps explain why ancient people regarded this unusual landscape as a sacred place.
Shizu-no-Iwaya has also played an important role as a place of worship. According to tradition, Shizuma Shrine was once enshrined inside the cave. A torii gate still stands near the entrance, providing a reminder of the site’s former religious significance.
Shizuma Shrine is said to have been founded in 886 and is recorded as an ancient shrine in the Engishiki, a major compilation of laws and religious institutions from the Heian period. The shrine enshrines Okuninushi-no-Mikoto and Sukunahikona-no-Mikoto, further emphasizing its connection with the ancient myths of land development.
Because the shrine stood close to the sea, it was repeatedly affected by high waves and heavy rainfall. In 1674, a landslide caused by heavy rain severely damaged the shrine buildings. The shrine was reportedly moved to the area around present-day Tarumiyama the following year.
Numerous foundation plaques and wooden votive records from the Edo period and later have survived at the shrine, offering valuable evidence of the long history of local worship and preservation.
Near the rear of the cave stands a stone monument commemorating the Man’yoshu poem, erected in 1915. Its title was written by Tokugawa Iesato, while the poem itself was inscribed in the calligraphy of Senke Taketomi.
The monument, standing beside the quiet coast and ancient-looking cave, creates a striking link between Japan’s literary heritage and its natural landscape. Here, mythology, poetry, geology, and history come together in a single setting.
Shizu-no-Iwaya is designated as a Natural Monument by Oda City and is also associated with the Japan Heritage story of Iwami’s volcanic history, titled “The Eternal History Told by the Volcanoes of Iwami: A Journey to Meet the Jomon Forest and the Silver Mountain.”
The Iwami region contains many distinctive geological formations created by ancient volcanic activity. Shizu-no-Iwaya is one of the most impressive examples, with its exposed rock formations preserving visible traces of the region’s geological past.
For travelers interested in geology and the formation of the Japanese landscape, the cave offers a fascinating opportunity to see how volcanic activity and marine erosion have shaped the coastline over millions of years.
The coastline surrounding Shizu-no-Iwaya features rugged rocks and beautiful views of the Sea of Japan. The sound of waves breaking against the shore creates a peaceful atmosphere, while the changing light adds to the cave’s mysterious character.
At sunset, the sea and sky can take on warm shades of red and orange, creating a particularly atmospheric scene around the cave.
For centuries, Shizu-no-Iwaya has been remembered as a setting associated with ancient gods, while the Man’yoshu preserves its literary connection. The site therefore offers a rare combination of natural grandeur and ancient Japanese cultural traditions.
Although entering the cave is currently prohibited for safety reasons, visitors can still appreciate its impressive exterior and imagine the extraordinary landscape that inspired generations of people.
From JR Oda-shi Station, Shizu-no-Iwaya can be reached by bus in approximately 10 minutes. Get off at the Shizuma Hiraguchi bus stop and continue on foot for about 20 minutes.
The walk toward the coast provides opportunities to enjoy views of the Sea of Japan and the surrounding natural scenery.
Because access inside the cave is currently prohibited, visitors should remain outside the restricted areas and follow all safety barriers and signs. With its ancient mythology, literary heritage, geological history, and dramatic coastal scenery, Shizu-no-Iwaya is one of Oda City’s most fascinating places to experience the mysterious connection between nature and Japanese culture.