The Paris Metro, short for Métropolitain, is a rapid transit system serving the Paris metropolitan area in Francilian, the region of France's capital. A symbol of the city, it is known for its density within the capital's territorial limits, as well as its uniform architecture and historical entrances influenced by Art Nouveau. The system is 245.6 kilometres (152.6 mi) long, mostly underground, as well as its 321 stations of which 61 allow the riders to transfer between the sixteen lines (with an additional four under construction and one in project), all numbered 1 to 14, with two extra branches, 3bis and 7bis, named such as they are former parts of Lines 3 and 7 respectively.