The Paris Métro or Métropolitain (French: Métro de Paris) is a rapid transit system that operates in Paris and Paris Metropolitan Area. A symbol of the city, it is noted for its density within the city limits and its uniform architecture influenced by Art Nouveau. The network is mostly underground and runs to 214 kilometres (133 mi) in length. It has 303 stations, of which 62 facilitate transfer to another line. There are 16 lines, numbered 1 to 14 with two minor lines, 3bis and 7bis. Lines are identified on maps by number and colour, and direction of travel is indicated by the destination terminus.
Paris's is the second busiest metro system in Europe, after Moscow. It carried an annual total of 1.524 billion passengers in 2011 (up from 1.506 billion in 2010), which translates into 4.175 million passengers a day. It is one of the densest metro systems in the world, with 245 stations within 86.9 km2 (34 sq mi) of the city of Paris. Châtelet – Les Halles, with 5 Métro lines and three RER commuter rail lines, is the world's largest metro (subway) station.