Costing almost 61 billion yuan ($9.2 billion), the newly constructed lines most connecting the distant and dusty suburbs to the city center bring Beijing's subway network to 336 km (209 miles).
That distance is just a fraction of what the city government has planned, the Beijing Municipal Commission of Transport said reporters at the unveiling of the city's No. 15 line.
Beijing aims to have a 561-km-long subway network by 2015, and is planning for between 700 and 1,000 km by 2020, Li Xiaosong, the deputy director of the commission said Reuters.