Odaira Cave (小平鍾乳洞) is located in Midori, Gunma Prefecture. It is about 93m long small carven that you can actually see the forming of stalactites.

Tourist Info.
There are parking and restroom.
Time: 9:00 to 17:00(Apr. to Sep.) 9:00 to 16:00, the last entry is 30 min. before the close time.
Admission: 310 yen for adults, 150 yen for kids. There is a group discount.
Closed: on Tuesday from Dec. to Mar. If it's holiday. Closed on the next day.

Access
0. at Isezaki Station.
1. use JR Ryomo Line to Shimo-Nitta Station.
2. use Watarasekeikoku Line to Omama.
3. walk northeast.