Koyasan is an alpine basin located about 1,000m above sea level. Surrounded by mountain peaks on all sides, it is 5.5km east-west and 2.3km north-south.
Kukai, known as Kobodaishi through his posthumous honorific name, sailed to China at the age of 31 in the year 804. In the ancient capital of Chang'an, he studied Tantric Buddhism under Priest Keika and was granted a master title. After returning from China in 806, he had been spreading the Shingon (True world) Sect of Buddhism.
He founded Koyasan as a religious retreat in 816, when the then Emperor Saga granted him the land. It is said that this was the start of Kongobuji Temple.
Kobodaishi started his eternal meditation in the cave of Okunoin on March21, 835, at the age of 62 and has been believed to appear his subtle body to the followers.
Today, there are 117 sub-temples besides two monasteries and Okunoin Temple that collectively create a fantastic atmosphere.
Koyasan is a treasure house of esoteric culture. There are over 40,000 which are recognized as cultural properties including 200 National Treasures and 40 Prefectural Cultural Properties.