Châtelet – Les Halles is the major commuter train hub in Paris. It is one of the largest underground stations in the World. Taken together with the Paris Métro stations Châtelet and Les Halles, to which it is directly connected, hosts 750,000 travellers per week day (including interchanges), 493,000 for the RER only. It is named after the Châtelet monument and the former market of Les Halles.
The station is served by lines A, B, and D of the RER, and is therefore directly accessible from many stations in Île-de-France. A large underground network is formed in conjunction with the Châtelet and Les Halles Métro stations. This network brings together three of the five RER lines and five Métro lines, and is the central node of the network of transit of the Ile-de-France metropolitan area. Every day, 750,000 travelers pass through Châtelet–Les Halles, including 493,000 just for the RER. At peak hours, the station can see 120 trains in just one hour.
Châtelet–Les Halles is also the station where the second part of the RATP-managed IMAGE project was installed, which consisted of 10 flat screens containing information on local traffic from all carriers (RATP, SNCF, etc.). The purpose of the project was to provide local information on rail traffic (next trains, traffic conditions, delays, etc.) that will eventually replace all previously existing information systems.