In Western Europe, the crusades in the 12th century expanded to preach the Catholic Faith and establish feudal states. Fortified towns at junctions of roadways got a functionally justified four-part layout similar to Jerusalem, where the Church of the Resurrection situated in the orthogonal intersection of the Cardo and the Decumanus. Lands on the Baltic Seacoast inhabited by the Balts and Finnish-Ugrian tribes came under the authority of Pope and Emperor of the Holy Roman Empire. Catholic church-states or bishoprics were founded. Western European cities became a model for urban planning in the newly established Riga Bishopric (1201–1255). At the beginning of the 13th century, the wall-fortified small semi-circular area of German town of Riga adjoined the Rīdziņa River became the main military economic base for the Baltics’ expansion and the most important commerce and spiritual power centre, where the administration structure and ownership of the most valuable land plots in a four-part layout medieval town at the junction of important traffic routes was the same as in other distant merchants’ cities in Europe. Research goal: analysis of four-part layouts of Riga and Lemsal (Latvian: Limbaži) medieval towns developed at junctions of important traffic routes. Research problem: the development of the Riga Bishopric’s early fortified town layouts and defense systems has not been sufficiently studied. Research novelty: the Riga Bishopric’s towns are analyzed in the context of Western European medieval urban planning traditions. Research methods: analysis of archive documents, projects and cartographic materials of medieval urban planning, study of published literature, inspection of buildings in nature.