Paris Métro

The Paris Métro or Métropolitain () is a rapid transit system in Paris, France. The network is mostly underground. It has 19 lines, which together are 225.1 km (139.9 mi) long. There are 304 stations. 17 of these lines are owned by RATP and 2 by Paris Airport. 
The Paris Métro is a symbol of the city. Notable is its Art Nouveau architecture at the older entrances. It is the second busiest metro system in Europe, after Moscow. It carries 4.16 million passengers a day, and an annual total of 1.52 billion (2015). 
The first line opened on 19 July 1900, during the 1900 World's Fair ("Exposition Universelle"). The system expanded quickly and the core was complete by the 1920s. Extensions into suburbs were built in the 1930s. The network reached saturation after World War II. The Métro introduced newer trains to allow higher traffic, but further improvements have been limited by the design of the network and in particular the short distances between stations. Besides the Métro, Downtown Paris and its urban area are served by a number of other transit systems.