Lake Tazawa(田沢湖,Tazawa-ko) is a caldera lake in the city of Semboku, Akita Prefecture, northern Japan. It is the deepest lake in Japan at 423 metres (1,388 ft). The area is a popular vacation area and several hot spring resorts can be found in the hills above the lake. Akita Prefecture's largest ski area, Tazawa Ski Area, overlooks the lake.