Dogashima Tensodo Cave – Izu Peninsula

Designated as a natural monument in 1935.

Tensodo is a cave made by the erosion of the tide and waves. A part of the ceiling of the cave has fallen out, and it looks like a skylight. The clear ocean reflects the light from the skylight and the appearance of shining the inside of the cave on the emerald is mysterious.

The ground just above is inside the Dogashima hiking course and you can also look at the hole from above. But the best thing is to visit the cave with the pleasure boat.