The knights of the Livonian Brothers of the Sword, applying new constructive means, built irregular layout fortified yards for support places and secular power centres in difficult available places. In Livonia, the first important fortified centre created by monks-knights was financially independent Wenden (Latvian: Cēsis) Castle on a cape to control the Gauja Waterway, significant trade routes and the settlement. After the heavy defeat on 22 September 1236 in the Battle of Saule, the knights of the Livonian Brothers of the Sword joined to the Teutonic Order which regulation determined that the convent had to live in monasteries. The knights of the Teutonic Order rebuilt fortified urban structures created by the Livonian Brothers of the Sword and established Commandry and Vogtei centres: four blocks formed a square or rectangular building around the courtyard. Research object: Segwold (Latvian: Sigulda) and Wenden castles in Livonia. Research goal: to discover the architecturally spatial uniqueness of Segwold and Wenden castles created by monks-knights in two different construction periods and the fortresses’ impact on the settlement planning. Research problem: in research of architecturally complicated solution of Segwold and Wenden castles complexes, it is necessary to understand the specifics of construction in chronologically different periods. Research novelty: analysis of the planning and spatial structure development of Segwold and Wenden castles built under traditions of two construction periods. Research methods: studies of archive documents, projects and cartographic materials of urban planning, published literature and inspection of buildings in nature.