Today 35.5 percent of the Albanian population is urban, 64.5 percent rural. The relatively low urbanization rate is probably a result of state restrictions on mobility. Virilocal marriage leads many Albanian women to live in urban areas. About 80 percent of the population today lives in apartment blocks built in the Socialist period. Besides the capital, Tirana, the main regional centers are Durrës (the main port), Shkodër, Elbasan, Vlorë, and Korcë. In presocialist days villages were composed of groups of houses surrounded by farmland and pastures. Stone and wood were the main materials used in house building. The Ottoman influence can clearly be seen in the widespread enclosure of houses by stone walls for Religious reasons and the use of stone, originally for defensive purposes, in the first floor, timber in the second. Also typical of Albania is the kula, a fortified dwelling of stone with slits for windows in the lower floor and closable windows above, adapted to the threat of brigandage, foreign (especially Ottoman) invasions, and, above all, feuds. The one-room house of stone and timber with a central fireplace is the basic unit, sometimes extended with additional buildings into larger farms. Because of the sloping terrain, many houses are built perpendicularly on several levels against the slope, thus utilizing all possible space. In areas with a more Mediterranean climate, a veranda added to the basic unit serves in summer as a place for cooking, sleeping, and living. In the south one also finds the manor houses of the former feudal rulers (patrons) in both rural and urban areas, some of which were built for defense. In the plains both these and ordinary houses often show the influence of Italian architecture.