Owakudani is an active volcanic valley with sulfurous steam vents (fumes), hot springs and hot rivers. Owakudani was created around a crater after the last eruption of Mt. Hakone about 3000 years ago. Steam vents and bubbling pools of water are seen from the walking trail and the smell of sulfur is in the air. Eggs cooked in the naturally hot water of Owakudani can be purchased. Their shells are blackened by sulfurous fumes. Each consumed blackened egg ("Kuro-Tamago") supposedly prolongs one's life by seven years. It is advised not to eat more than two and a half of these blackened eggs.