Cyanoprokaryotes are considered pioneers of biological colonization of rock substrates in various environmental conditions. They are able to successfully develop on granites in the northern climate. In our study in the city Vyborg cyanoprokaryotes were found on granite rapakivi. They developed most actively in the spring, when snow melts. Their species composition has been established. Cyanoprokaryotes were found on many buildings in Vyborg, as well as on granite outcrops within the city (Park Monrepo). In St. Petersburg, such biofilms were found at a number of historical sites.