The 13th to 14th centuries were a period of significant urbanization. Paris was the largest city in the realm, and indeed one of the largest cities in Europe, with an estimated population of 200,000 or more at the end of the century. The second-largest city was Rouen; the other major cities (with populations over 10,000) were Orléans, Tours, Bordeaux, Lyon, Dijon, and Reims. In addition to these, there also existed zones with an extended urban network of medium to small cities, as in the south and the Mediterranean coast (from Toulouse to Marseille, including Narbonne and Montpellier) and in the north (Beauvais, Laon, Amiens, Arras, Bruges, etc.). Market towns increased in size and many were able to gain privileges and franchises including transformation into free cities ("villes franches"); rural populations from the countrysides moved to the cities and burgs. This was also a period of urban building: the extension of walls around the entirety of the urban space, the vast construction of Gothic cathedrals (starting in the 12th century), urban fortresses and castles (such as Philip II Augustus' Louvre around 1200), bridges, etc.