Kan'ei-ji is a Tendai Buddhist temple in Tokyo, Japan, founded in 1625 by Tenkai. The main object of worship is Yakushiruriko Nyorai (薬師瑠璃光如来). Because it was one of the two Tokugawa bodaiji (funeral temple; the other was Zoujou-ji) and because it was destroyed in the closing days of the war that put an end to the Tokugawa shogunate, its name is inextricably linked to that of the Tokugawa shoguns. Named after the Kan'ei era during which it was erected, this great complex used to occupy the entire heights north and east of Shinobazu Pond and the plains where Ueno Station now stands. It used to have immense wealth, power and prestige, and it consisted of over 30 buildings. The Shinobazu Pond itself and the Bentendo temple which stands on its island used to be an integral part of Kan'eiji. Tenkai, liking Lake Biwa, had Benten Island built in imitation of Chikubushima, and then the Bentendo on it. At the time the island was accessible only by boat, but later a stone bridge was added on the east, making it possible to walk to it. The temple was destroyed during World War II, and the present one is just a reconstruction.
The temple and its numerous annexes were almost completely destroyed during the Boshin War's Battle of Ueno and never restored. The site where it once stood was confiscated and is presently occupied by Ueno Park. What is today the temple's main hall was taken from Kita-in in Kawagoe (Saitama Prefecture) and transferred to the site of a former Kan'ei-ji subtemple.
Many temple structures had already been destroyed in the great Mereiki fire of 1657. A new hall was constructed inside the enclosure of Kan'ei-ji in 1698.
Tenkai wanted to create a powerful religious center and, to achieve that, he built Kan'ei-ji imitating Mount Hiei's Enryaku-ji. The temple was therefore erected north-east of Edo Castle to ward off evil spirits that were believed to come from that unlucky direction, and was named after the era it was built in, like Enryaku-ji. Tenkai's project enjoyed from the beginning the shogunate support, so much so that Tokugawa Hidetada in 1622 donated the land on which it was built. At the time, on that land there were the suburban residences of three daimyos, (Toudou Takatora of the Tsu domain, Tsugaru Nobuhira of the Hirosaki domain and Hori Naoyori of the Murakami domain), but the land was expropriated and donated to Tenkai for the temple. He was also given 50 thousand silver Ryo and a building as a contribution.
The chief abbot's residence, the Honbou, was built in 1625, which is considered the year of foundation of the temple. After that, several daimyos contributed with the construction of other buildings. The main hall, called as in Enryaku-ji's case Konponchuudou, was finished only in 1697.