Passengers and the platform reflected in a train's windows at Taiyanggong Station. The Beijing Subway is the second largest metro system in the world. Opened in 1969, it now consists of 17 lines with more than 232 stations and an average of 9.5 million daily commuters. To accommodate the growing number of users, extensive expansion plans are set to more than double the network by 2020. Seventy-five percent of the global population is projected to be living in cities by the middle of this century. Panos photographers explore this mass urban shift through a nine month social documentary project through topics such as urban farming, eco-housing, technological innovations, elastic environments, children at play, green spaces, economic divides and much more.