Chagpori, the "Iron Mountain", is the small rocky hill directly opposite the Potala, separated from it by a saddle now crossed by Beijing Middle Road. Until 1959 the summit was occupied by the Mentsikhang, the Tibetan Medical College founded in 1696 — the building was shelled during the Lhasa uprising and never rebuilt. A radio mast stands in its place.
The hill is still venerated as the spirit-mountain of Vajrapani, and on its lower slopes you'll find one of the most photographed sights in Lhasa: a rock face densely carved and painted with Buddha images, the rock paintings of Chagpori. Pilgrims circle a small chapel here and slip past makeshift altars in tiny caves. Climb up the path that branches off toward the radio tower for the classic photograph of the Potala framed by prayer flags.