The lake is situated on the border between Aomori and Akita Prefectures, roughly midway between the Pacific Ocean side and the Sea of Japan side, at an elevation of 401 meters.
It is a collapsed caldera lake of the Nasu volcanic ash group. The central cone, which erupted along the southern shore, was divided into two peninsulas — Nakayama and Okura — by Nakanoumi, an inner lake formed through a second collapse. Together with the mountain stream of the Oirase River and the alpine highland beauty of the Hakkōda Mountains, the area is a tourism destination of international renown. The lake is also well known for its kokanee salmon (*himemasu*) aquaculture.