A bastide is a fortified town. They were built mainly in the south of France in the Middle Ages. Most bastides were built between 1229 and 1373, between the Albigensian Crusade and the Hundred Years' War. Today, there are about 400 bastides. They all have a central square, and a rectangular street layout. On the market square, the houses have arcades. They were usually built in places that were easy to defend, such as the top of a hill or on a plain.