Blue water
Dark and clear.
Makoto Nakashima — CC BY 2.0 · Original uploader (WT-fr) Newton4ever at French Wikivoyage — Public domain · Miya.m — CC BY-SA 3.0 · lienyuan lee — CC BY 3.0 · lienyuan lee — CC BY 3.0
Lake Mashu is an endorheic crater lake in the caldera of a potentially active volcano, in Akan Mashu National Park on Hokkaido in northern Japan, about 68 km northeast of Kushiro in a straight line. The Ainu call it Kamuy-to, and it has been called the clearest lake in the world. Steep crater walls 200 metres high surround the lake, which has no significant inlets and no outlet and is one of the deepest in Japan. On 1 August 1931 its water clarity measured 41.6 metres, the basis of its claim to be the world's clearest; since the 1950s it has ranged between 20 and 30 metres. In summer fog often hides it, about 100 days a year, giving it a reputation for mystery. Dark, clear blue water fills a round basin between towering green walls, with a small island in the middle and a pointed volcanic peak on its shore, and on clear days white clouds are mirrored on its surface. Visitors stand at viewpoints on the crater rim, as there is no way down to the water. The lake can vanish entirely behind fog, so morning or autumn, when the air is clearer, is best.
Dark and clear.
In the middle.
Often hides it.
Akan Mashu National Park, Hokkaido, Japan
No.
Morning or autumn.