There is a tradition in Nagano prefecture to renew the pillars at the Suwa Grand Shrine every six years. In order to do this, there is a special event to bring sixteen suitable logs down the mountains by riding them. The average log weighs about 10 tons and is extremely dangerous while gaining speed, which doesn't seem to frighten the participants off.
The festival lasts for several months and is divided into two main parts: first one deals with the log riding and is called Yamadashi in the upper shrine Kamisha (early April) and the second one is in charge of the pillar renewal process, and is called Satobiki in the lower shrine Shimosha (May). Both parts are extremely dangerous for participants. However, this festival still is one of the biggest and most famous events in Nagano!