Lake Ashi (Japanese: Ashinoko) was formed in the caldera of Mount Hakone after the volcano's last eruption 3000 years ago.
Today, the lake with Mount Fuji in the background is the symbol of Hakone.
The best views of the lake in combination with Mount Fuji can be enjoyed from Moto-Hakone, from the Hakone Detached Palace Garden and from the sightseeing boats cruising the lake.
Note however, that clouds and poor visibility often block the view of Mount Fuji, and you have to consider yourself lucky if you get a clear view of the mountain.
Visibility tends to be better during the colder seasons of the year than in summer, and in the early morning and late evening hours.
Two companies, Hakone Sightseeing Boats and Izuhakone Sightseeing Boats, operate boats between Moto-Hakone and Hakone-machi at the lake's southern shores and Togendai and Kojiri at the lake's northern end. A boat cruise from one end of the lake to the other takes roughly 30 minutes and costs 970 yen.
The Hakone Free Pass is valid on the pirate ship shaped Hakone Sightseeing Boats but not on boats operated by Izuhakone.