Île-de-France tramway Lines 3a and 3b are the first modern tramway in Paris proper, since the 1937 closure of the previous comparable system. They are operated by the RATP ("Régie autonome des transports parisiens") and divided into two sections called T3a and T3b. The line is also known as the "Tramway des Maréchaux" because it follows the Boulevards of the Marshals, a series of boulevards that encircle Paris along the route of the former Thiers Wall (built from 1841 to 1844). The boulevards are, with three exceptions, named for Napoleon's First Empire marshals ("maréchaux"); they were transformed by redevelopment works carried out during the two and a half year construction of the line, which opened on 16 December 2006 under the designation T3.