Kasumigaura is a large, shallow lake in southeastern Ibaraki Prefecture. It's Japan's second largest freshwater lake, after Lake Biwa. It has an area of 168 square kilometers (65 square miles) and a circumference of 137 kilometers (85 miles). Even at its deepest point, it only measures 7 meters (23 feet).

The lake is fed by the Tone River--Japan's second longest--and forms part of the Suigo-Tsukuba Quasi-National Park. It's home to over 40 species of fish, including the freshwater smelt and whitebait.