芥屋の大門, Sea cave in Itoshima, Japan.
Keya no Ohto is a massive sea cave carved into basalt cliffs that extends roughly 90 meters into the rock and rises about 64 meters high. The entrance spans around 10 meters wide and displays striking columnar rock formations with natural hexagonal and octagonal patterns throughout.
The basalt formations took shape millions of years ago through volcanic activity that built up this coastline. Since then, sea erosion has gradually hollowed out the rock to create the massive cavern visible today.
The site holds deep significance for the local fishing community, who have built their port and livelihoods around these waters for generations. The cave stands as a landmark that defines the identity and daily rhythm of people who work here.
The best way to experience the cave is by boat departing from Keya port, with regular service during the warmer months of the year. Plan to arrive early and dress appropriately for sea conditions, as weather can change quickly over the water.
The cave ranks among Japan's largest basalt caverns, but its true scale becomes apparent only when approaching from the water inside. Many visitors are surprised at how the sense of size transforms once you enter from the boat.
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