Dewa Sanzan is the name used to refer to the three mountains Mount Haguro, Mount Gassan and Mount Yudono. It was at Dewa Sanzan that Shugendo (a religion that amalgamates the indigenous practice of mountain worship with Buddhism, Taoism, Confucianism, etc.) originated. Being a central place of worship for many Buddhist sects, Dewa Sanzan was also known as the “Mountains of the Many Buddhist Teachings” (Hashukengaku) in the Kamakura period.