This is the headquarters of the Shingon sect and the residence of Kōya-san's abbot. The main gate is the temple's oldest structure (1593); the present main hall dates from the 19th century. It's free to enter the grounds, but costs ¥500 to enter the main hall, which has several fusuma (opaque paper sliding doors) adorned with landscape paintings by famed 17th-century artists, including those of the Kanō school. Many of the temple's statues and ritual implements are displayed at the Reihōkan.
From inside the main hall you can see the banryutei (1984), Japan's largest rock garden. It contains 140 large granite stones brought from Shikoku (Kōbō Daishi's birthplace) and white gravel from Kyoto, which are collectively meant to represent two protector dragons rising from a sea of clouds.
The more recently built annexes (Betsuden and Shin-Betsuden) contain contemporary paintings of seasons and images inspired by Kōbō Daishi's sojourn in China.