The Beijing Metro, the world’s busiest and second longest subway system, officially turned 50 last month and it remains one of the best ways to get around the city, with over 670km of track delivering an average of 10.5 million trips per day. The oldest metro system in China commenced service on Oct 1, 1969 as part of Beijing's celebration of the 20th anniversary of the founding of the PRC. While today it seems like Beijing opens a new metro line every year, constructing the initial line was not easy. It took 15 years from conception until the first cars rolled under the Beijing streets and three decades would pass before there was a Line 2.