that point the boundary largely follows the ring road south, with a few diversions to take in all of the exit ramps at the Jianguomen Street interchange and some open land at the Tonghui River to its south. At Longtan Park in the southeast corner of the district, it curves west with the road to form the district's southern boundary with the Fengtai District. Just past Temple of Heaven Park, in the Yongdingmen area, it leaves the ring road to take in a roughly triangular area to the south that includes the Beijing South railway station at its eastern corner. It then follows Yongdingmen, Tianqiao and Qianmen streets due north back to the southern end of Tian'anmen Square. There it turns west briefly, then goes up the square's west road between the China Numismatic Museum and the Great Hall of the People. At the square's north end is West Chang'an Avenue. Physical Like most of Beijing, the district is consistently level, with an elevation of above sea level, reflecting the city's location on the North China Plain. There are a few significant bodies of water, all lakes in parks—Liuyin Lake in that park and Youth Lake in Qingnianhu Park, both in the district's northern portion, and Dragon Lake in Longtan Park at the district's southeast corner. On the west central edge is the moat surrounding the Forbidden City. The Nanchang River, heavily channelized from its days as the once-walled city's north moat, flows across the district's north, with the South Moat paralleling the 2nd Ring Road along its southern boundary. Along the southern edge of the Forbidden City another small stream, the Changpu River, flows above ground for a kilometer. Much of the district is densely developed, with major streets following a grid plan, while the side streets connecting them are irregular. Temple of Heaven Park is the largest, at , with the Temple of Earth Park in the Hepingli Subdistrict in second. In addition to the parks already mentioned, others of note include Dongdan Park off that street in the central area of the district and Nanguan Park near the northeast corner. Some major arteries also have wide planted median strips. The Russian embassy complex just inside the Ring Road at the northeast corner of the district also has another large planted area, although it is fenced off. The most significant non-park urban open space in the district is