A symbol of the city, it is noted for its density within the city limits and its uniform architecture,
influenced by Art Nouveau. It is mostly underground and 214 kilometres (133 mi) long. It has 303 stations, of which 62 have transfers between lines. 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 terminus.
It is the second-busiest subway system in Europe, after Moscow. It carried 1.541 billion passengers in 2012, (up from 1.524 billion in 2011), 4.210 million passengers a day. It is one of the densest metro systems in the world, with 245 stations within the 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.