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 is a popular tourist site for its scenic views, volcanic activity, and especially, Kuro-tamago (黒卵 lit. "black egg"?) — a local specialty of eggs hard-boiled in the hot springs. The boiled eggs turn black and smell slightly sulphuric; consuming the eggs is said to increase longevity. Eating one is said to add seven years to your life.
Access to Ōwakudani is via a funitel, the Hakone Ropeway. There is also a road to a visitor's center just below the Kuro-tamago hot springs site. Most visitors hike the roughly 1 kilometer trail or take the Hakone Ropeway to the actual site where the eggs are boiled to participate in the ritual egg eating. The funitel offers a vast view of both Mount Fuji (on clear days) and the sulphur vents just below the visitor's center. Present day activities surrounding sulphur vents are the result of massive land slides in the past, construction of concrete barriers and stabilization of the area have been under way for many decades.
The tourist site in Ōwakudani was closed in May 2015 due to volcanic activity and re-opened on April 27, 2016. However, people suffering from Asthma, Bronchitis, Heart Disease, people who are using heart pacemakers and pregnant women are advised not enter the valley because of high volcanic activity. .
Coordinates: 35°14′31″N 139°01′14″E / 35.241916°N 139.020667°E