Overview: Winter in Hokkaido Prefecture... It's a fascinating time to visit for the stunning snowscapes and natural phenomena caused by the severe cold. Kussharo, located in a huge caldera, is part of the Akan-Mashu National Park. Cradled by the outer rim of the crater, heavy, cold air accumulates and the temperature plummets below minus 20 degrees Celsius on windless days. Lake Kussharo is the largest lake in Japan that completely freezes over. Hot springs gush out from many spots, releasing steam. Snow, ice and the steam interact in the ultra-low temperatures to create mysterious and stunning natural works of art.