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Japan, Hokkaido, Lake Mashu-Ko, Lake surrounded by mountains

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Considered by many to be Japan's most beautiful lake, Mashū-ko once held the world record for water clarity. The island in the middle was known by the Ainu as the Isle of the Gods. A road runs along the western rim. You can't get down to lake level, but there are two official viewing points called Viewpoint 1 and Viewpoint 3; there's no parking fee at the latter.