Lake Mashu in Akan National Park in the eastern part of Hokkaido is a caldera lake formed by an eruption about 7,000 years ago. The lake is famous for its beautiful water, which is one of the clearest in the world, and the fog that envelopes its surface as is sung in a popular ballad “Misty Lake Mashu” of 1960s.

Of all the peaks that are forming the outer rim of this caldera, the highest one is Mt. Mashudake (858 m), also known as Kamuinupri (god’s mountain). Mt. Mashudake presents its imposing view right in front of the first observatory of Lake Mashu. The walking trail is built from the first observatory to the summit. Walking along the ridge of the outer rim, you will go under the tunnel of dense foliage and enjoy viewing pretty alpine plants as well as mirror-like surface of Lake Mashu, which repeatedly come into and go out of sight. As there is very often a thick fog on the surface of the lake, you may not be able to see it. If the fog is not very thick, you may have a chance to enjoy the mystic atmosphere of the lake with the mysterious island of Kamuisshu in its center.