The largest of the Gelugpa monasteries was the residence for lesser lamas. Founded in 1416, it was enlarged in the 16th century by the Second Dalai Lama. By the era of the Fifth Dalai Lama it had become the largest monastic institution in the world, with 10,000 residents. During the Cultural Revolution it suffered only minimally, because the Army used the building as its headquarters and therefore didn't ransack it as much as other temples. The monastery was reopened in
1980, although the number of resident monks has been severely depleted.
The monastery's most important building is the Tshomchen, whose vast assembly hall, the Dukhang, is noteworthy for its 183 columns, atrium ceiling, and ceremonial banners. Chapels can be found on all three floors, as well as on the roof. In the two-story Buddhas of Three Ages Chapel (Düsum Sangye Lhakhang), at the rear of the Dukhang on the ground floor, the Buddhas of past, present, and future are each guarded by two bodhisattvas.