In Western Europe, the crusades were expanded in the 12th century to preach the Catholic Faith and to establish feudal states. Fortified towns at road junctions, where the crossing point of two highways was a natural meeting-place for trade might occur, got a functionally justified four-part layout similar to Jerusalem, where the Church of the Resurrection in the orthogonal intersection of the Cardo and the Decumanus situated. Lands on the Baltic Seacoast inhabited by the Balts and Finnish-Ugrian tribes came under the authority of the Pope and Emperor of the Holy Roman Empire. Catholic church-states or bishoprics were founded. Western European cities organized around the church and the marketplace at the centre became a model for urban planning in the newly established Bishopric of Riga. At the beginning of the 13th century, the wall-fortified small semi-circular area of the German town of Riga adjoined the Rīdziņa River and became the main military-economic base for the Baltics’ expansion and the most important commerce and spiritual power centre. The administrative structure and ownership of the most valuable land plots in a medieval town of the four-part layout at the junction of important traffic routes were the same as in other distant merchants’ cities in Europe. Research goal: analysis of four-part layout medieval towns of Riga (Latvian: Rīga, Livonian: Rīgõ) and Lemsal (Latvian: Limbaži) developed at junctions of important traffic routes. Research problem: the development of layout and the defensive system of the Riga Bishopric’s early fortified towns have not been sufficiently studied. Research novelty: 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, the study of published literature, an inspection of buildings in nature.