Wikipedia
Microdistrict, or microraion (, , ), is a residential complex—a primary structural element of the residential area construction in the Soviet Union and in some post-Soviet and former Communist states. Residential districts in most of the cities and towns in Russia and the republics of the former Soviet Union were built in accordance with this concept.
According to the Construction Rules and Regulations of the Soviet Union, a typical microdistrict covered the area of 10–60 hectares (30–160 acres), up to but not exceeding 80 hectares (200 acres) in some cases, and comprised residential dwellings (usually multi-story apartment buildings) and public service buildings. As a general rule, major motor roads, greenways, and natural obstacles served as boundaries between microdistricts, allowing an overall reduction in city road construction and maintenance costs and emphasizing public transportation. Major motor roads or through streets were not to cross microdistricts' territories. The entrances to a microdistrict's territory were to be located no further than 300 meters (1000 ft) apart.
Standards also regulated the accessibility of the public service buildings (excluding schools and pre-school facilities) by imposing a 500-meter (1,500–foot) limit as the farthest distance from any residential dwelling. One of the city-planners' tasks was to ensure that the fewest number of public buildings was built to cover the microdistrict's territory in accordance with the norms. Typical public service structures include secondary schools, pre-school establishments (usually combined kindergarten and nursery), grocery stores, personal service shops, cafeterias, clubs, playgrounds, and building maintenance offices, as well as a number of specialized shops. The exact number of buildings of each type depended on the distance requirement and the microdistrict's population density and was determined by means of certain per capita standards.