Abstract: Buildings in urban area are situated in patterns - blocks, streets, quarters etc. These patterns can be studied by various spatial techniques. After introduction of one special type of spatial correlation, we will analyze the built up structure in Prague. The correlation has algebraic fade-out which means, that buildings are not randomly situated, but there exist a long-range dependence preserving the structure. To support this fact we costruct a white-noise analog of Prague urban area having the same density profile where such correlation is not presented. Orientation preferences in the urban structure (greater North-West and South-East correlation) will be also discussed.