CRT Line 6 is the second heavy rail subway line in Chongqing, as well as being the longest rapid transit line in China, at 85.6 km (53.19 mi) long. It opened with provisional revenue service on September 28, 2012, and connects Nan'an, Yuzhong, and Jiangbei districts in central Chongqing.

Chongqing is a municipality in Southwestern China. Chongqing is one of the four direct-administered municipalities under the Central People's Government, along with Beijing, Shanghai, and Tianjin. It is the only directly administrated municipality located deep inland. The municipality covers a large geographical area roughly the size of Austria, which includes several disjunct urban areas in addition to Chongqing proper. Due to its classification, the municipality of Chongqing is the largest city proper in the world by area, though it does not have the largest urban area.