Owakudani Valley — Active Volcanic Fumes and Black Eggs

Owakudani (大涌谷, 'Great Boiling Valley') is an active volcanic valley where sulfurous fumes vent from fissures in the rock, creating a moonscape of yellow-stained cliffs, bubbling hot springs, and the overwhelming smell of hydrogen sulfide. The valley formed 3,000 years ago during the eruption that created Lake Ashi, and it remains geothermally active — a reminder that Hakone sits atop a restless volcanic system.

The valley's main attraction beyond the otherworldly geology is kuro-tamago (黒玉子, 'black eggs') — chicken eggs boiled in the sulfurous hot springs, which turns the shells jet black while the interior remains normal white-and-yellow. Local legend claims eating one black egg adds seven years to your life; they're sold at the valley's souvenir stands (¥500/five eggs, sold only in fixed quantities). The Hakone Ropeway passes directly over the valley, providing aerial views of the steaming vents before arriving at Owakudani Station where visitors can walk among the fumes.