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Fuji-Hakone-Izu NP, Shizuoka
Claim this place to tell your story your way.
A spider’s web once helped Minamoto no Yoritomo escape into Tensodo—at least in local legend. The tale says he hid in a passage supposedly reaching Kamakura, while the web fooled pursuers into thinking nobody had gone inside.
The skylight is a natural roof-collapse opening about 18 m above the water; daylight reaches far enough into the cave for boats to pass without lamps. The seawater shifts color with season, time and weather.
Three entrances feed Tensodo’s maze: 2 face Suruga Bay and 1 opens inland. Cross-passages connect the chambers, and the broad main branch stretches 147 m—so this is far more than a simple sea tunnel.
In early spring 1935, poets Yosano Tekkan and Akiko each wrote a tanka about Tensodo. Tekkan imagined the cave as a temple and invited a monk friend to chant a sutra; Akiko made spring light falling through its skylight her subject.
The pale rock around Tensodo is volcanic, not limestone: nearby Dogashima cliffs preserve ash and pumice deposited by eruptions beneath an ancient sea. Waves later carved the cave into the fine-grained tuff.
Japan designated Tensodo a National Natural Monument on August 27, 1935. Its official record highlights not just its beauty, but its unusually complex cave structure and the clearly visible faults that helped shape it.
