As a result of variations in ecological conditions and Inheritance practices, there have been large variations between Villages in different parts of the country. Traditionally, the largest villages were in Dalecarlia, in the valley of Norrland, and on the rich plains of Skåne. There are also variations in the form of the villages. In Dalecarlia the houses have often been built in irregular and open clusters ( klungbyar, cluster villages). In other parts, the villages have had a more closed and regular structure, as for example in Svealand and Gotaland where the villages were often built as a row of houses ( radbyar, row villages). In Skåne the villages have often been constructed around an open place ( rundby, circle villages). There have been five main forms of traditional housing design in the Swedish villages. The northern Swedish farmyard consisted of several buildings around a grassy yard. In the central Swedish yards the main house and the farmhouse were separated by a building, often a stable with a gate. The third type (Gothic) had a long, rectangular form, with the farmhouse separated from the main house by a fence. The western Swedish type was an irregular and loose construction of houses. The southern Swedish farmyard consisted of four long row houses built together. These square houses in Skåne were built with brick, and clay was applied over a stick frame. In the rest of the country, wood has been the most common construction material. Houses built in contemporary Sweden are basically the same throughout the country. Because of urbanization many empty houses are now used as summer houses. The relatively few castles and manors are found only in southern and central Sweden.