Homes in Alsace are never built isolated, except in the mountains. It results from the population density, which exceeds 200 inhabitants per square kilometer in the region. Despite this data, the houses are always independent of each other and never share a party wall. Each village has retained its typical central square with a water fountain. There is often a wall around the city, as in Riquewihr. The exterior facade of the houses is highly regulated by the architects of the Bâtiments de France (official building control). The red terracotta roof tiles are, for example, still very present in the villages.