Which city has the largest metro system?

By route length, the world’s largest metro systems are in China, where Shanghai and Beijing each operate more than 800 kilometres of lines. Remarkably, Shanghai’s first metro line only opened in 1993, making its growth one of the fastest in transport history. The oldest metro is the London Underground, whose first section opened on 10 January 1863 using steam trains. The New York City Subway has the most stations of any system, with 472 counted by its operator, and much of it runs 24 hours a day. China now has dozens of cities with metro systems, most built within the past 25 years.