Milan’s urban growth was heavily influenced by the structure of the rail network for transporting goods and people. The great railway yards that used to service the industrial system have now lost their raison d'être after the relocation of industrial plants and the tertiary sector dynamics took over the city. These have become large abandoned brownfields or soon to be abandoned, totaling over 1,300,000 square meters, located mainly along the urban belt surrounding the city walls, often in densely built environments. Since 2005 these areas were the subject of several agreements between the City of Milan, State Railways SpA (FS) and the Lombardy Region, to examine various scenarios and the feasibility of their conversion, as confirmed in the draft of the new Territorial Government Plan (PGT), which identifies the Areas of Urban Transformation. Scenarios and assumptions that, in the current revision of the PGT, must approach the strategic role of this rich heritage from an environmental regeneration and valorization perspective extended to urban and metropolitan scales.