Lake Okotampe is a mysterious lake that, along with Onneto near Lake Akan and Lake Shinonome near Lake Shikaribetsu, is considered one of the three most mysterious lakes in Hokkaido.
Located at the western foot of Mt. Eniwa, the lake has a circumference of 5 km and a maximum depth of 21.1 m. It is surrounded by thick virgin forest, and the color of the lake water appears to change from emerald green to cobalt blue depending on the weather, viewing angle and time.
The forests around Lake Ocotampe are mixed coniferous and deciduous broadleaf forests. In order to preserve this diverse and pristine natural forest, it has been designated as a Forest Ecosystem Protection Area (Forest Act).
It is also designated as a special protection area in Shikotsu-Toya National Park (Natural Park Law), preserving the rich natural environment. Lake Okotampe can be viewed from the observatory on the side of Road 78.