Cobalt-blue crater-lake Ashi-no-ko was created by an eruption of Hakone-yama nearly 3000 years ago. It's famous for the view of Mt Fuji, reflected on the still waters, visible on clear days (winter mornings are your best bet, but Fuji is ever-fickle). Sightseeing boats, departing from the pier at Moto-Hakone, travel to the best viewing points.