The Paris Métro, short for Métropolitain, is a rapid transit system serving the Paris metropolitan area in France. A symbol of the city, it is known for its density within the capital’s territorial limits, uniform architecture and historical entrances influenced by Art Nouveau. The system is 245.6 kilometres (152.6 mi) long, mostly underground. It has 321 stations of which 61 have transfers between lines. The Métro has sixteen lines (with an additional four under construction), numbered 1 to 14, with two lines, Line 3bis and Line 7bis, named because they used to be part of Line 3 and Line 7, respectively. Three lines (1, 4 and 14) are automated. Lines are identified on maps by number and colour, with the direction of travel indicated by the terminus. The Métro is operated by Régie autonome des transports parisiens (RATP), which also operates part of the RER network, light rail lines and many bus routes. It is the second-busiest metro system in Europe, as well as the twelfth busiest in the world. It carried 1.476 billion passengers in 2024, roughly 4.04 million passengers a day, which makes it the most used public transport system in Paris. It is one of the densest metro systems in the world, with 244 stations within the 105.4 km2 (41 sq mi) of the City of Paris. Châtelet–Les Halles, with five Métro and three RER commuter rail lines, is one of the world’s largest metro stations. The system generally has poor accessibility since most infrastructure was built before accessibility standards emerged, and few stations have been retrofitted. We celebrate this feat of engineering with an AI image of the Metro …