The block under intervention was occupied by several buildings, of which the PT building stands out, the building at the corner of Rua do Raio and Rua de São Lázaro and the building on the corner of Avenida da Liberdade and Rua Dr. Gonçalo Sampaio. In the construction of the new development, most of the buildings were demolished, except for the PT building, the main facades of the CTT building and the building located at the corner of Rua do Raio and Rua de São Lázaro. The PT building, since it houses several land-based networks and communications equipment fundamental to the city, was preserved and maintained operational in all phases of the work. Thus, the solutions of excavation and peripheral containment have been defined in order to guarantee total accessibility and functionality. Based on the evaluation of the existing constraints, the solutions for the following work fronts were studied and implemented in an articulated way: foundations, structures and underground network.