Geological feature in Kumejima, Okinawa, Japan. Nationally Designated Natural Monument since 2014. Located on the south coast of Oujima (Ou Island), connected to Kumejima by a bridge. Comprises about one thousand pentagonal and hexagonal rocks, 1 to 1.5 meters in diameter. Formed during the Miocene period by columnar jointing of andesitic lava. Water erosion has leveled and smoothed the rock tops. # Why Go 🌊 See unique hexagonal and pentagonal rock formations 🌋 Witness natural phenomenon of cooled andesite magma 📸 Great photo opportunities, especially at low tide 🚶 Easy access to Ou Island via bridge # Tips 💡 Best viewed at low tide, check daily tide charts.