The building stock of the large urban centers within Greece includes several mass housing complexes, which have been built during the first two post-war decades. A 95% of the state-planned housing complexes are a work of the Workers’ Housing Organization (Οργανισμός Εργατικής Κατοικίας, Ο.Ε.Κ.) (Gouvousi in Housing Complexes in Greece and their prospects, Phd thesis. A.U.Th., Thessaloniki (in Greek) 2011). The designing principles of modernism are evident in the architecture of the buildings designed by the architecture department of O.E.K., in their typological and morphological characteristics, as well as in the overall urban planning of the settlements. In social housing complexes, built by O.E.K., thanks to the appropriate design, the housing needs were more effectively met than in the most common type of middle-class mass housing unit in Greece (polykatoikia). Large free spaces, low building density and the functional layouts of the apartments are to this day important features that improve accommodation in the dwellings, compensating for their limited area. The majority of mass housing complexes in Greece are poorly to moderately preserved.