Mount Osorezan (恐山) is ranked along with Koyasan and Hieizan as one of Japan's three most sacred places. It was discovered over 1000 years ago by a Buddhist priest in search of a sacred mountain that resembles the world of Buddha. Today, it is the site of Bodaiji Temple.
Osorezan is translated as "Fear Mountain", a name that comes in part from the mountain's exceptional landscape. The area is rich in volcanic activity, and a strong smell of sulfur permeates the air. The ground is gray and barren and marked by openings that steam, bubble and blow hot water. Lake Usori, located next to the temple, is colored various shades of blue due to its high sulfur content.