Located on the Baltic Sea coast, “Gdynia Modernist City Centre” encompasses the two most significant east-west and north-south streets, featuring interwar planning blocks and the majority of the city centre’s preserved buildings from that period, which reflect the large-scale application of modernist ideas in architectural design. The result is an urban organism that harnesses a building-block-based planning approach to develop a characteristic, compact complex of modernist architecture, with robust individual architectural expressions. The city centre, with its buildings, villas on Kamienna Góra hill, and other residential buildings of this period, illustrates a critical break with historicism in the progression of turning the village of Gdynia into a new major sea gateway of the first Polish Republic between the First and Second World Wars.