The ghosts of Oku-no-in, cemetery and spiritual heart of Mount Koya, have a long time to wait: 5,670,000 years, give or take. According to the scriptures of Japan's Shingon sect of Buddhism, that's when the faithful expect the "Buddha of the Future" to arrive in this vibrant mountaintop monastic community. In the meantime, Mount Koya, headquarters of the sect, attracts thousands of adherents and tourists each year.

The faithful come to pray or leave a little ash of a loved one near the tomb of Kukai, the founder, so that they may be present that fateful day. For tourists, the promise of a glimpse into the living traditions of Japan's rich spiritual history draws many looking for something more than standard temple tourism.

Kukai, whose tomb is the focus of Mount Koya, founded the eponymous monastery in 816 after returning from China as a full master of Esoteric (secretive, magical) Buddhism. Posthumously known as Kobo Daishi (the Great Saint), Kukai was one of Japan's early geniuses. He was immensely active: dissatisfied with contemporary Japanese Buddhism, he brought back dramatic Esoteric ritual from China and created his own sect, Shingon, affecting Japan's entire social landscape in the Heian Period (794-1185). He also engineered dams, introduced a new style of calligraphy to Japan, spoke Chinese well enough to compose poetry, and wrote more than 50 books on literature, philosophy and religion. That's not accounting for his legendary exploits. Apart from the usual starving of oneself on mountain peaks, thousands of folk tales surround his life, ranging from his disputed creation of hiragana and katakana to slaying dragons and throwing his vajra, a ceremonial mace modeled after a lightning bolt, from China, and later finding it in the branches of a pine on Mount Koya. You can still see a young descendant of that pine tree among the temples today, for despite its long history, much of Mount Koya is new.