Considering the Prince Lakeside Annex in Hakone?
A VT member wrote the following comment about visiting Hakone:
Owakudani by CitizenTed
This active crater is worth the trouble of multiple transport links to get there. A great, steaming mountain shrouded in sulfurous mist. Be sure to buy some eggs boiled black in the hellish waters. They add 7 years to your life. Really.