Thiers wall
In addition, the Boulevard Périphérique, the beltway surrounding Paris, was built on the site of the ruins of the Thiers wall, a short distance 'outboard' from the Boulevards of the Marshals. However, it is more like a motorway than a boulevard. Île-de-France tramway Lines 3a and 3b run along the Boulevards of the Marshals, nearly encircling Paris since 3b opened in December 2010, on the sixth anniversary of the opening of 3a along the southern section.