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.[1]

It is a popular tourist site for its scenic views, volcanic activity, and kuro-tamago (黒卵, lit. «black egg») — a local specialty of eggs hard-boiled in the hot springs.[2] The eggs turn black and smell slightly sulphuric; eating one is said to add seven years to your life.[3]