Owakudani is a volcanic valley with active sulfur 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 — a local specialty of eggs hard-boiled in the hot springs. The boiled eggs turn black and smell slightly sulfuric; consuming the eggs is said to increase longevity. Eating one is said to add seven years to your life. You may eat up to two and a half for up to seventeen and a half years, but eating a whole third is said to be highly unadvised.
Access to Owakudani 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 to the actual site where the eggs are boiled to participate in the ritual egg eating. The funitel offers a stunning view of both Mount Fuji (on clear days) and the sulfur vents just below the visitor's center. Present day activities surrounding sulfur 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.