The Paris Subway System, also known as the METRO, is a rapid transit system that serves the city of Paris and its suburbs. It consists of 16 lines and over 300 stations, making it one of the largest METRO systems in Europe. The METRO is operated by the Regie Autonome des Transports Parisiens (RATP) and is used by millions of people every day. It is an efficient and affordable way to get around the city, and is a popular tourist attraction.