Legend has it that Kobo Daishi, the founder of Shingon Buddhism, threw his sankosho (a double ended, three pronged Buddhist ceremonial tool) from China, where he had been studying, toward Japan. Back in Japan, while in search of a place to headquarter his new religion, he came across his sankosho stuck in the branches of a pine tree on Koyasan and started construction of the Garan, Koyasan's central temple complex, there. The pine tree, that caught the sankosho, is still growing there.
The two most prominent buildings of the Garan are the Kondo Hall and the huge Konpon Daito Pagoda. The Kondo Hall is a large wooden temple hall where major ceremonies are held. The building has burned down multiple times over the centuries, and the current hall dates back to 1932. It enshrines an image of Yakushi Nyorai, the Buddha of medicine and healing.
Next to the Kondo Hall stands the vermilion Konpon Daito Pagoda, a 45 meter tall, two tiered, tahoto style pagoda. A statue of the Dainichi Nyorai (Cosmic Buddha, also known as Variocana), the central Buddha in Shingon Buddhism, stands in the middle of the pagoda's interior and is surrounded by statues and paintings on pillars, which together make up a rare three dimensional mandala (a metaphysical map of the cosmos). Mandala are usually two dimensional paintings.
Kobo Daishi started building the Kondo Hall and Daito Pagoda, however he was not able to finish them himself. His successors completed the construction of the two main structures and also expanded the grounds of the Garan with multiple additional halls and pagodas over time. Among these are the Toto (eastern pagoda), Saito (western pagoda), Miedo (founder's hall) and Koya Myojin Shrine, which enshrines Mount Koya's local kami (Shinto deities).