Hakone is famous for its hot springs which I strongly recommend.

This is a picture of Yumoto, the entrance to the Hakone area near Odawara. It is Hakone's most famous hot spring with a particularly long history, high quality water and numerous baths and inns. But many more hot spring baths can be found in the valleys and mountains of Hakone and at the shores of Lake Ashi.

Transportation:

A convenient way of getting to Hakone is transfering from Shinjuku Station and buying a special ticket for the "Odakyu Romancecar (ロマンスカー)." This is a limited express train that takes you south-west of Tokyo, to mountain resorts such as Gotenba and Hakone as well as beaches such as Numazu and Enoshima.