The purpose of this paper is to consider a number of valuable architectural accomplishments from the beginning of the XX century, built in Vienna (1919-1933) and Frankfurt am Main (1925-1931), by means of Aldo Rossi’s theoretical thought and analytical approach. Through the author’s re-drawings of selected case studies, it is possible to analyse the relevance of housing in the construction of the city and the fundamental role of the typology and morphology. Of the European experiences Das rote Wien and Das neue Frankfurt developed the most convincing typological solutions in answer to issues raised by housing problems in the nineteenth century. They correspond to two opposite urban and typological models: the large courtyard block (Hof) and the slab formation block (Siedlung). In this regard, Aldo Rossi provided a thorough examination concerning housing typology showing a particular interest in Vienna and Frankfurt examples: for instance, the article Un piano per Vienna published in Casabella Continuità 277 (1963); some essays on typological features in Aspetti e problemi della tipologia edilizia (1964); The Architecture of the City (1966); and Neues Bauen in Deutschland (1973), edited when he was professor at the ETH Zurich. He also investigated the 1920s housing examples through the relationship between “socialist realism” and “architectural rationalism”. The main purpose of this contribution is to propose a comparative analysis between the housing projects built in Vienna and Frankfurt that present inspiring and relevant qualities concerning morphology, density and typology. The study is conducted through critical re-drawings of the Höfe and Siedlungen typological assemblage plans by employing the same graphic code in order to get the highest degree of homogeneity and comparability. On the one hand, the purpose is to produce new and original analytical documents – in line with Rossi’s attitude about the project knowledge as necessary instrument –, on the other hand, to demonstrate that these dwelling complexes, even though they were designed almost one hundred years ago, are a fundamental presence within the contemporary city and offer key insights relevant to today’s housing design. The significant teaching of the Vienna and Frankfurt housing initiatives consists in their critical attitude to building the city through typological research, that they posit as an essential element for the society. Architectural historians and critics have often neglected or looked at these examples from a mere ideological perspective. Thanks to Rossi’s contribution about the observation of the city assumed as “urban artifact”, today, it is possible to investigate these typological solutions using a new approach which intends to better comprehend 1920s’ social housing experiments and, thus, provide a wider understanding. To sum up, the comparative approach has two goals: on the one hand, it establishes a homogeneous instrument that could efficiently be applied to several other housing cases in order to increase the studies and the research concerning this topic; on the other hand, it stresses the importance of morphological and typological research within the contemporary housing debate and architectural design.