The Onbashira is a once-every-seven-years festival held in Suwa on a steep hill. Is it held to celebrate the renewal of the Suwa Taisha shrine. It involves lots of crazy Japanese men riding a giant log down a really steep hill. Ok, there's a bit more to it than that, but for the purposes of entertainment it is very much lots of crazy Japanese men riding a giant log down the really steep hill.
A video of this years festival can be found here > www.youtube.com/watch?v=Tbtdzefvqjo.