The large-dimension housing complexes in Rome have grown since the late ‘60s as a result of the 1st PEEP planning of 1964. The plan tried to face the large housing emergency caused by the rising urbanization (Albano, 2001). The peripheral areas of the city started to be filled with several neighborhoods in sharp break with the close urban fabric: high-density neighborhoods that for conformation and urban characteristics were placed in contrast to the existing compact city. This discontinuity is highlighted by urban scale designing approach, described by wide spaces for gardens and high speed roads, separating isolated great-size buildings. Approaching the city as an organism in constant evolution in space and time (Piccinato, 1941) and composed of continuous additions and modifications (Rossi, 1966), these neighborhoods resulted immediately as amorphous objects, autonomous from the continuity of the existing city and isolated from the network infrastructure. Nowadays, after about forty years, they still live in strong isolation conditions, becoming the focus to look at for urban regeneration interventions. The proposal article suggests a comparison between the great-size neighborhoods and the conventional compact ones by the analysis of different density data (floor area ratio, population density, cubic meter built on the covered area, green area ratio) in order to stress the morphological differences for the possibilities of transformation. The transformability of some case of studies (CastelGiubileo, VigneNuove, Pineto, PrimaPorta, Torevecchia) are analyzed up to the building scale, through modeling correlating structural and technology performances with the morphological characters.