Owakudani

Ōwakudani lies on the northern flank of Kanmurigatake, one of the central cones of the Hakone volcano, at an altitude of roughly 800 to 1,000 metres. It is the largest of Hakone's fumarole fields: a bare, yellow-grey slope where volcanic gas, steam and hot water escape from the ground, leaving crusts of sulphur and a strong smell of hydrogen sulphide.

The valley was created in two stages about 3,100 and 2,900 years ago, when a steam explosion caused a large landslide and a small pyroclastic flow built the cone of Kanmurigatake. The name means 'great boiling valley'; its older name, Ōjigoku, meant 'great hell'. Steam and hot water from Ōwakudani are piped down to supply many of the hot-spring inns of Gōra, Sengokuhara and other parts of Hakone.

The site is a stop on the Hakone Ropeway, part of the classic loop through Hakone by mountain railway, cable car, ropeway and sightseeing boat on Lake Ashi. From the ropeway and the station area, the view extends over the steaming slopes to the cone of Mount Fuji when the weather is clear.

Ōwakudani has been active throughout recorded history, with minor explosions, mudflows and shifting vents. Hot-spring development and tourism grew from the Meiji era, when Hakone became a resort for Yokohama and Tokyo, and the ropeway made the valley one of its most popular sights.

In 2015 increased seismic activity led the Japan Meteorological Agency to raise the volcanic alert level; a very small phreatic eruption occurred near the valley in late June, and access was closed for over a year. Since then, gas levels and access are managed by the town of Hakone and the prefecture, with gas warnings broadcast in several languages.

For centuries the steaming valley was seen as a gateway to hell, and figures of the bodhisattva Jizō, protector of travellers and souls, were placed along the old paths. The black eggs sold at the site, boiled in the volcanic water, have become Hakone's best-known souvenir and a lighthearted continuation of the association with long life.

The valley also illustrates Japan's everyday relationship with volcanoes. The heat that makes Ōwakudani dangerous feeds the onsen of Hakone, one of the country's oldest resort areas, and the site doubles as an outdoor classroom where visitors can see volcanic processes at close range.