In Rome, Emperor Constantin I started to build the most ancient cathedral – the five-nave Archbasilica of St. John in Lateran, but the Lateran Palace was given as a present to Bishop of Rome for his residence. Perimeter building blocks set up the building complex. In Europe, during the 6th–9th centuries numerous rulers proclaimed Christianity as the only religion in the country. The Church strengthened its impact on the society and governmental administration. In Rome, like in Jerusalem, a religious centre was created, but in the middle of the 8th century, a city-state Vatican was founded, and on one of hills, the Pope’s residence was placed. Christians organized structures governed by Bishops and founded Catholic church-states – bishoprics. In the late 12th century, subjugation of the lands populated by the Balts and the Finno-Ugric tribes began. Bishoprics and cult centres were founded, and residences for Bishops and Canonical Chapters were envisaged. The bishopric main building was the cathedral. In Europe during lots of centuries evolution of the cathedral building-type happened. In the Balts and Finno-Ugric lands cathedrals were affected by local building traditions. The origins of the Riga Cathedral (Latvian: Rīgas Doms) can be found in 1201–1202, when the bishopric centre from Üxküll was moved to the newly-founded Riga, where the Bishop’s residence was built on a geopolitically and strategically convenient place. The most important centres to look for inspirations were Braunschweig, Westfalen, Köln, Lübeck, Ratzeburg, Bremen, Hamburg. Research problem: interpretations of sacral building typology and terminology application cause difficulties in the research of historical building plans. Research topicality: evolution of the cathedral building-type and impact of cathedral building complexes on formation and planning of medieval urban structures during the 13th and 14th century. Goal of the research: analyse planning of historical structure in urban centres of bishoprics to determine significance of cathedrals as architectural dominances in spatial composition of towns. Research novelty: this research is based on Latvian historians and archaeologists’ former studies. Nevertheless, opportunities provided by the analysis of urban planning and cartographic materials have been used, and created building due to local construction traditions has been assessed in the European context. Results: study of architecture, layout formation and structure of cathedrals on the southern Baltic Seacoast lands during the 13th and 14th centuries. Main methods applied: this study is based on research and analysis of archive documents, projects and cartographic materials of urban planning, as well as study of published literature and inspection of buildings in nature.