Mashu Lake is the clearest lake in Japan, and is located at the eastern edge of Akan National Park in Kawakami County, the eastern of Hokkaido.  It has a world record of visibility. In 2001, it was designated as a Hokkaido Treasure.

Rising 858 meters at the southeast edge of the lake, isKamuinuburi (Mt. Mashu), which means ‘the mountain of the god’.  Mashu Lake is a ‘caldera lake’, which was formed following a big eruption 7,000 years ago. Because of that, the lake is surrounded by cliffs. It has no rivers connected; the water is augmented  by rain and a springand leaks through its surrounding walls.  The water in Mashu Lake is used in surveys to measure air pollution.

Each of theobservation decks aroundthe lake offersgreat views.  It is especially the mirror-clear reflections of sky, clouds and mountains on the surface of the lake, that will make you release a shutter.

There is a famous anecdote that says fortune will knock at your door if you encounter ‘Mashu Lake in fog’, but you would be better off visiting this lake on a fine day.