Chongqing, also known as Shancheng, Jiangcheng, Wudu, and Qiaodu, is a municipality directly under the central government of the People's Republic of China, a national central city, a mega city, and a central city in the eastern Sichuan region. The city covers an area of 82400 square kilometers, with a permanent population of over 30 million, making it the city with the largest population in the world's listed areas.
Chongqing has a mountainous terrain, with many buildings and transportation built on uneven mountainous terrain, resulting in buildings that cannot be level, roads that cannot be level, and limited building area, resulting in a high density of buildings.