The inner city is divided into eastern and western halves by Dongcheng and Xicheng Districts. The Forbidden City, where emperors once lived, and Tiananmen Square, the center of the city, both belong to Dongcheng. But the Zhongnanhai Compound, next door to the Forbidden City, where China’s current leaders now reside, and the Great Hall of the People, on the west side of Tiananmen Square, both are part of Xicheng. The outer city, adjacent and south of the inner city, comprises the former Xuanwu and Chongwen districts, merged with Xicheng and Dongcheng respectively in July 2010. Chongwen is home to the Temple of Heaven. Xuanwu is oldest continuously inhabited part of Beijing. Some of its neighborhoods including those around the Niujie Mosque (b. 996 A.D.) and Pagoda of Tianning Temple (b. 1119 A.D.) predate the Yuan capital. Unlike in most other parts of the city, most narrow lanes in Xuanwu are called "jie" instead of "hutongs". Each of the two core city districts has population density of over 20000 persons/km2 (51800 persons/sq. mi.)