Paris has the most closely spaced subway stations in the world, with 245 stations within the 41 square kilometres (16 sq mi) City of Paris. Supposedly you are never more than 400 meters from a subway station.
Paris is the second busiest metro system in Europe after Moscow. It carries 4.5 million passengers a day. Châtelet Les Halles is the world's largest underground station.
During construction of the new driverless line 14 in 1990, several canoe-shaped boats were found ten meters below the banks of the Seine river. The boats date back to 2800-2500 BC, making them among the earliest signs of human settlement in the area. They are now housed in the Carnavalet museum.