Mt. Omuro is a volcano form about 4,000 years ago. The height of the mountain is about 580m. The crater is about 1km around and 70m deep.

There is a Sengen Shrine on the top of mountain. Unlike other Sengen Shrine, it enshrines only Iwanagahimenomikoto.

Yamayaki (Burning the mountain)
Yamayaki has history of over 700 years. It is held in 2nd Sunday of February. The tradition started as burning bugs and prevent them coming out to the farms in spring. There are two ceremonies. First, they burn the inside of the crater in the morning. Then, they burn the entire mountain from the bottom at noon. It will takes only 10 to 15min. to finish burning.

http://www.i-younet.ne.jp/~oh-murol/