The Yama-age festival is said to data from 1560, when Suketane Nasu, the
lord of the Karasuyama castle deified Susano-no-mikoto, the brother of the
Su-goddess to drive out the plague.
Yama (litarally mountain) are stage settings section used as a background.
Made of enormous Karasuyama Japanese paper and flour paste, they are
transformed into grand mountains.
For 3 days about 150 people are necessary to operate them.
http://www.youtube.com/watch?v=hbMF9xPR6Rk