Lake Suwa (諏訪湖, Suwa-ko?) is located in the center of Nagano Prefecture in Japan. It is the twenty-fourth largest lake in the country in terms of area.
Lake Suwa is the site of the "traces of the gods" (御神渡り, o-miwatari?), a rare natural phenomenon. The lake has a natural subsurface hot spring so that when the lake freezes in winter, the water under the ice is warm and continues to flow. This results in ice pressure peaks that can reach heights of up to 30 cm or more. The local belief is that these ridges are formed by the god Takeminakata (en), who came from the upper sanctuary of Suwa (Suwa-taisha kamisha) to join his beloved, the goddess Yasakatome, residing at the lower sanctuary of Suwa (Suwa-taisha shimosha).