Ōwakudani

Ōwakudani (大涌谷, lit. "Great Boiling Valley") is a volcanic valley with active sulphur vents and hot springs in Hakone, Kanagawa Prefecture, Japan. It was created around 3,000 years ago, as a result of the explosion of the Hakone volcano.

It is a popular tourist site for its scenic views, volcanic activity, and kuro-tamago (黒卵, lit. "black egg") — a local variety of hard-boiled eggs that uses the hot springs in their preparation. As a result of them being boiled in the mineral-rich waters of the valley, which contain high levels of sulfur, the egg shells turn black and give off a slightly sulfuric odour; eating one is said to add seven years to your life.

Upon seeing the hellish scenery, when Kōbō Daishi visited Owakudani more than a thousand years ago, he offered prayer to Bodhisattva. The Enmei-jizō in Owakudani is said to have its origin in the prayer.