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 created around 3000 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 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.
Upon seeing the hellish scenery when Koubu Daishi visited Owakudani more than a thousand years ago, he offered prayer to Bodhisattva. The Enmei-jizo in Owakudani is said to have its origin in the prayer. 
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 used to hike the roughly 1 kilometer trail which has been closed since 2015 due to increased volcanic activity, or take the Hakone Ropeway to close to 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, but not fully, as it is still not possible to walk close to the steaming vents due to the hazards involved. Also, 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. .
- "Owakudani - Hakone Travel Guide | Planetyze". Planetyze. Retrieved 2018-02-21.
- "Hakone Ropeway". Hakone Ropeway. Retrieved 2015-11-17.
- Animal Science (2015-05-06). "Alert Raised at Japan's Hakone as Earthquakes Continue". WIRED. Retrieved 2015-11-17.
- "Volcanic Activity in Hakone". Jnto.go.jp. Retrieved 2015-11-17.
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