Hiking in the area is popular.
The most popular courses through the little islands that dot the southern shore start from near Onuma Koen station, and the time-pressed can even opt for a 15-minute circuit. Ask at the tourist office for a map.
Paddle boats and row boats are available to rent.
Mt. Komagatake
This volcano dominates the scenery, but the mountain has been off-limits to climbers recently.
There are many hot springs scattered around the shores of the lake.