The physical history of any building is linked to time, the choice of materials and the mechanical stresses on them. Especially for ancient buildings, to the construction and destructive events that characterized their life cycles. The case of the Porta Maggiore (Rome), monumentalization of a part of the Claudian aqueduct, seems to hold these requirements. Today, the structure appears as a rather simple and easily recognizable elements, but the analysis of the architectural phases following the first structural stage reveals a certain fragility. The main causes include the use of materials with different mechanical properties than the original ones, compounded by addition and demolition work that clearly changed the original structural balance. The analysis here proposed provides a general review of the issues that should be addressed to a comprehensive structural assessment that can be helpful for potential consolidation interventions. In this sense, the archaeological perspective and reconstruction of the building phases is used to understand the structural dynamics that Porta Maggiore (more generally, the aqueduct) had to face.