The winter palace of the Dalai Lamas from 1649 to 1959, has been a museum since then, and is a World Heritage Site since 1994. The palace is named after Mount Potalaka, the mythical abode of the bodhisattva Avalokiteśvara. The 5th Dalai Lama started its construction in 1645. It may overlay the remains of an earlier fortress called the White or Red Palace on the site, built by Songtsen Gampo in 637.
The building measures 400 meters east-west and 350 meters north-south, with sloping stone walls. Thirteen floors of buildings, containing over 1,000 rooms.