The Beijing city wall was a series of fortifications built between the early 15th century and 1553. The Inner city wall was 24 km long and 15 meters high, with a thickness of 20 metres at ground level and 12 metres at the top. It had nine gates. This wall stood for nearly 530 years, but in 1965 it was removed to allow construction of the 2nd Ring Road and the Line 2, Beijing Subway. Only one part of the wall is extant, in the southeast, just south of Beijing Railway Station. The Outer city walls had a perimeter of approximately 28 kilometres. The entire enclosure of the Inner and Outer cities formed a "凸" shape with a perimeter of nearly 60 kilometres.