This mysterious lake shows many faces like emerald green and dark blue, as its color changes. Lake Onneto, which is situated 623m above sea level, is part of Akan National Park (east of Ashoro Town), one of the three great secret lakes in Hokkaido. The lake was created when the river was dammed up due to the volcanic eruption of Mt. Meakan-dake, and the name, “Onneto” means old pond or big pond in the original Ainu language. Since its surface beautifully changes color depending on the time of day or the season, the lake is also called Goshikinuma.