The coastal areas of the Baltic Sea were subjugated, applying military forces – monk-knights’ orders. In the conquered Prussian, Livs and Latgalian lands administrative centres were founded. On places appropriate for economic activity, fortified houses were built. Building complexes formed medieval urban structures. A strategic building for land conquest was a tower castle, which originally had a quadrangle planning. The residential tower was included in the fortified building complex, and the construction volume obtained vertical emphasis for the defence function. In Livonia, a castle with a tower house by traffic routes and market place was built, and settlements formed origins for the medieval urban planning. In Prussian four-block fortresses with a tower were built for administrative centres, but in trading cities the Town Hall with a tower construction dominated. Previous researches: Estonian art hist. Prof. Dr. ph. Armin Tuulse (1907–1977) published the first profound research on Livonian fortresses “Die Burgen in Estland und Lettland” (1942). Since 1999, historical, archaeological, architectonical research materials of German fortresses have been collated in series “Latvian Medieval Castles” published by History Institute of Latvia and in archaeologist Prof. Dr.hab.hist. Andris Caune and Dr. Ieva Ose’s “Lexicon of German Castle in Latvia from late 12th–17th century” (2004). Architect Prof. Friedrich Lahrs’ (1880–1964) research on Konigsberg Castle with a dungeon is dedicated to Prussian fortress architecture. One of the most recent researches is Prof. Dr. hab. Tomasz Torbus’ “The Architecture of Castles in the Prussian State of Teutonic Order” (2016). Evolutionary analysis of Prussian and Livonian fortified housing planning and structure during 13th–16th century has not been carried out in the regional and European context, and impact of medieval urban planning has not been assessed.