In what year did the eruption occur that laid down the lava upon which a famous forest visible from the Tenjō-Yama Park Mt. Kachi Kachi Ropeway? 
Tenjō-Yama Park Mt. Kachi Kachi Ropeway:  The observatory has a view of the lake, as well as Aokigahara forest, and Mount Fuji.
i don't know