登別温泉 大湯沼 北海道 Noboribetsu Oyunuma Hokkaido JAPAN ♨

Noboribetsu 登別市 (Ainu: nupur-pet) is a city in Iburi Subprefecture, Hokkaido, Japan. From the valley, there are attractive walking trails through the wooded hills above Noboribetsu. If you follow them for about 20 to 30 minutes, you will get to Oyunuma, a sulfurous pond with a surface temperature of 50 degrees Celsius and a smaller, even hotter, mud pond nearby.
The name, Noboribetsu derives from an Ainu word, nupur-pet, which means dark-coloured river.