The M4 extends from the San Cristoforo station to Linate Aeroporto for a total of 21 stations. (Fig. 1) As it traverses from the western to the eastern outskirts, nearing the city center in the central section, the route is intricately divided into functional lots with distinct construction priorities. Policreo has played a pivotal role, developing functional and architectural designs for 7 stations, including San Babila, Tricolore, Susa, Argonne, Forlanini FS, Repetti, and Linate Aeroporto. Our expertise extends to related shunting rods, the Idroscalo ventilation building at the line’s eastern end, and surface and road systems for Forlanini FS and Linate Aeroporto stations. We’ve crafted designs for finishes, integrated furnishings, and user orientation signage across all 21 stations. The structural design of Forlanini FS and Linate Aeroporto stations, both underground and above-ground, along with two interlocking structures, is also part of the project.