Of all areas of Mississippian culture, settlement patterns may be one of the most well understood. Mississippian houses tend to be small (approximately 3 meter by 5 meter), rectangular nuclear family dwellings. Communities seem to be of four primary kinds: (1) religious/political centers with multiple pyramidal platform mounds (often within a discrete "elite" area) and a community palisade or fortification system; (2) single-mound towns, often also palisaded; (3) villages of several to several dozen houses; and (4) hamlets of only one or a couple of houses. These community types are thought to have been organized into a settlement hierarchy in some Mississippian regions, with each type of community playing a particular role in the settlement system. Those roles were generally related to subsistence or other aspects of the economic system, and hence there is a common thread running through much of the research on Mississippian settlement, subsistence, and economic organization focused on the reconstruction of Mississippian "settlement-subsistence systems."