The city walls of Pisa were built, in their entirety, over about a century and a half: construction began in 1154 in the part of the city north of the Arno and continued until the year 1161, with subsequent completion in 1284 in the part of the Old Citadel area. In the area south of the Arno, the walls were built in 1186. Between the fifteenth and sixteenth centuries, other interventions took place with the construction of embankments, towers, and the raising of some sections. An analysis of historical photos shows that the walls still formed a border between town and country in the early twentieth century. After the last war, modern artefacts also occupied the vacant areas outside the city walls, in particular the areas to the east of the city, from today’s Via Vittorio Veneto to today’s Via del Borghetto, where the city walls are no longer visible and are almost totally enclosed by private areas. As part of the plan of sustainable urban development interventions, the Walls Project completed in 2018 was not only a tool for the redevelopment and protection of an important monumental system, but a true urban project, which interprets, through the articulation of the layout of the walls, the entire historic city, creating relationships, spin-offs and synergies with the spaces and architectural complexes inside and outside the walls. The restoration, conducted by arch. Marco Guerrazzi, stands as an ambitious project of urban significance that, through punctual restoration work and new functionalisation of the summit walkway, allows the lost continuity of the city walls to be rediscovered. Among the topics addressed, in addition to the punctual restoration works of the wall palimpsest, is the functionalisation of the summit walkway, useful for creating new synergies and connections between the consolidated city and the city outside the walls. A project that, operating inside and outside the city walls, tends to connect architectural emergencies, parks, urban and peripheral areas. The essay intends to critically examine the restoration work planned, and in part implemented, for the city walls of the Tuscan city and their adjacent parts, evaluating their sustainability in relation to the current needs and directions of restoration.