Jigoku(地獄) means hell and Dani/Tani(谷) means valley. This place is literally a valley of hell. It is a crater and located in Noboribetsu city which is one of the most famous Onsen place not only in Hokkaido but also Japan.
There is a round walking road, 600m length, which is available from May to November. Closed in winter.
There are many gushing points and fumaroles which make water hot and the part of hot spring to Noboribetsu hot spring.
The walking road is lighted up in the night. This is very mystic sight and there is a festival named ‘Noboribetsu Jigoku Matsuri'(登別地獄まつり) in the end of August, the last Saturday and Sunday of the month. This is nice and worth looking.
If you visit to Noboribetsu and stay in Ryokan or Hotel for Onsen, you should go there. Don’t miss it.