The history of Hakone Onsen began with Hideyoshi's attack of Odawara Castle. He used Hakone Onsen for healing his soldiers. Also, Tokugawa Iemitsu used this onsen for you bath room.
Hakone Yumoto is very famous for its Ajisai, Hydrangea. In the end of June, many people visit Hakone Yumoto to enjoy Ajisai. There are many hiking courses which you can enjoy Ajisai, and Hakone Tozan Line is popular as the Ajisai Train.