In the age of ancien régime, the process of growth and transformation of the city, mainly repla-cements, additions, changes, divisions, operated in continuity with the existing fabric: a growth that never completely severs the ties with the past. However, in cases of sudden loss of portions of the urban fabric, such as major fires and earthquakes, the voids became an opportunity to set a new way of thinking about the city. This is what happened in London after the fire of 1666 or in Italy after the earthquakes between the Seventeenth and Eighteenth centuries: in Sicily after 1693, in L'Aquila, to a lesser extent, after 1703. The reconstruction of the great void created in Lisbon after 1755 earthquake was perhaps even more radical: a regulation to rule the actions of private individuals was created, rather than thinking about monuments. An alternative model, in the late Eighteenth century, is the great utopia of Piranesi, who imagined a city made only with monuments to fill the great void of the Campus Martius in Rome.