Zento-in
Two theories exist about the origin of Zento-in: that it was the residence of Saicho’s disciple Ennin (794–864), and that it was constructed by Enchin (814–891) in order to honor the attainments of Ennin.
The name “To-in” is used for the dwelling of monks who have traveled to Tang China. In Hiezan there are two To-in halls, the Zento-in and Goto-in, one for Ennin and one for Enchin. Ennin went to China first, so his residence is called the Zento-in (literally the Earlier Tang China Temple). Enchin went to China after Ennin, and thus his hall is the Goto-in (literally the Later Tang China Temple).
Saicho, the founder of Enryakuji, asked Emperor Kanmu for permission to visit Tang China in order to receive the Buddhist Law directly from a master of the Tendai school, and to establish a center of Buddhism on Mount Hiei upon his return. Permission was granted, and he set out in 804, travelling throughout China for eight months in search of the Dharma, the universal truth proclaimed by the Buddha. Saicho studied Tendai and Zen, was initiated in esoteric Buddhism, and returned with many Buddhist scriptures. Kukai (774–835), who left for Tang China with Saicho, returned to Japan two years later with a greater knowledge of Esoteric Buddhism.
After Saicho passed away in 822 at the age of fifty-six, his disciples sought to acquire more esoteric Buddhist scriptures. In 835 when he was already aged forty-two, Ennin was given permission by the emperor to visit Tang China, and he departed in 838. He spent fourteen years travelling in the country and returned to Japan with 802 volumes of commentaries on the sutras, mandala images, relics of the Buddha, and Buddhist ritual implements. The long and arduous journey is documented in his famous diary, Records of a Pilgrimage in Search of the Dharma in China. The Zento-in houses some of these texts along with a statue of Ennin, and serves as his memorial.
Zento-in (Earlier Tang China Temple)
Goto-in (Later Tang China Temple)
Records of a Pilgrimage in Search of the Dharma in China (Nitto gubo junrei koki)