Shima Potholes (四万温泉の甌穴群, shima ouketsugun) are located on the south side of Shima Onsen. They are designated as a Natural Monument of Gunma Prefecture. There are 8 holes which were created by the water of the Shima River over a period of 10,000 years. One of potholes is 2m wide and 4m deep.

Tourist Info.
There is parking available.
Caution: When you hear the buzzer, the Shimagawa Dam will release its water. So, evacuate to high ground as soon as possible.

Access
0. at Nakanojo Station.
1. use local bus to Shima Onsen.
2. walk south (50 min.)