A new and perhaps last significant chapter in the history of socialist urban design is marked by the completion of “Split III”, the extension of the main Dalmatian centre for 50,000 inhabitants. Conceived by Slovenian planners Marjan Bežan, Vladimir Mušič and Nives Starc (built between 1971 and 1978), the project radically changes the planning strategies that had characterized, until then, the former Yugoslavia and more generally the Eastern European context. The project is the result of a curious and unique synthesis of seemingly irreconcilable urban theories: American and British theories developed between the 1920’s and 1940’s (from Clareance Perry’s Neighborhood theory to the different enhancements of the Garden City models), the contemporary mega structure experiments and the rediscovery of the seminal issues of the 19th century urbanism, above all the Camillo Sitte urban studies, carried out in Der Städtebau nach seinen künstlerischen Grundsätzen, that entered to Slovenia thanks to Plečnik’s teaching. The paper will explore the origins and the backstage of this methodological approach.