A steaming valley of sulphur vents left by Hakone's last eruption 3,000 years ago, reached by ropeway with Mount Fuji behind it on a clear day. Eggs boiled in the spring water turn black and are sold four for 500 yen, not the five most guides still say. The nature trail is open but on a guided, reservation-only basis, which is the point nearly everyone gets wrong in both directions.