Lake Mashu

Background

Lake Mashu lies in Teshikaga Town, Kushiro Subprefecture, Hokkaido, within Akan-Mashu National Park. It is a caldera lake, with a surface 351 metres above sea level, a maximum depth of 211.5 metres and an area of about 19 square kilometres, surrounded by steep crater walls about 200 metres high. On 1 August 1931 its water transparency was measured at 41.6 metres, the basis of its claim to be the clearest lake in the world; since the 1950s transparency has generally ranged between 20 and 30 metres. Kamuishu Island in the middle of the lake is a lava dome. The lake's original Ainu name was Kintan-kamuy-to, "lake of the mountain god", shortened to Kamuy-to, "lake of the gods"; later the Japanese came to call it after the neighbouring peak, Mount Mashu. Fog covers the lake for about 100 days a year, adding to its air of mystery.

Local customs

• Viewing the lake and the caldera cliffs from the observation decks
• hiking the Mount Mashu trail to the summit
• seeing the frozen lake and snowfields in winter.

Travel tips

• Fog is frequent, so whether you see the lake surface clearly is a matter of luck
• check the local weather before you go. There is no settlement on the lakeshore, so arrange meals and accommodation around Teshikaga.
• Head first towards Kushiro or Memanbetsu, then take a bus or rental car to Teshikaga and the observation decks
• bus times are subject to official announcements. The lake freezes from December to April
• fog is more frequent in summer, and clear weather gives you the best chance of seeing the surface.