Lhasa, the traditional capital of Tibet, is one of the highest cities in the world, sitting at an elevation of roughly 3,650 meters (11,975 feet). Its name translates to 'Place of the Gods.' The city is dominated by the Potala Palace, the former winter residence of the Dalai Lama, which contains over 1,000 rooms and is built into the side of Marpo Ri hill. Because of the high altitude, the air in Lhasa contains only about 68% of the oxygen available at sea level, which often causes altitude sickness for unprepared visitors. Lhasa is the spiritual heart of Tibetan Buddhism, centered around the Jokhang Temple and the Barkhor circumambulation path where pilgrims perform traditional prostrations. Despite modern modernization and the arrival of the world's highest railway (the Qinghai-Tibet Railway), Lhasa maintains a unique atmosphere of ancient devotion. The surrounding Tibetan Plateau is the source of many of Asia's major rivers, including the Yangtze, Yellow, and Mekong rivers.