Neighborhood classification for the 20 biggest cities in Finland, created from 250x250 m grid cells and data on the type of most typical buildings, the construction year of the neighborhood, and information on whether the neighborhood belongs to a city center. Includes seven classes of neighborhood types: centers (ClassId 1), blocks of flats from the 1950s and before (ClassId 2), blocks of flats from the 1960s and 1970s (ClassId 3), blocks of flats from the1980s and 1990s (ClassId 4), blocks of flats from the 2000s (ClassId 5), low-rise neighborhoods built before the 2000s (ClassId 6), and low-rise neighborhoods built after 2000 (ClassId 7). Each separate neighbourhood has an unique identifier (NeighborhoodId).