Lake Biwa in Shiga Prefecture is well known for being the biggest lake in Japan. It serves most of drinking water in Kansai Region. Lake Toya in Hokkaido, Lake Ashi (Ashinoko) in Hakone and Lake Kawaguchi at the bottom of Mt Fuji are all popular sightseeing spots. You’ll see some options of sightseeing cruises on the lakes. Lake Nojiri is another popular spot especially among foreign visitors to escape the heat in Japanese summer.