Although it may be thought that the rehabilitation of historical structures is a concern of modern engineering, studies on intervention processes from the past allow us to understand that this is a work carried out frequently and sometimes as a solution to low budgets for the construction of new buildings, or the need to offer quick practical solutions. The objective of this article is to show the way in which during the second half of the 18th century several important architectural and structural rehabilitation works were carried out in the walls of Cartagena de Indias, in view of the damage caused by the enemy attacks to the city as well as continuous impact by nature. By making use of primary sources (plans and original reports), the way in which two of the interventions were executed can be reconstructed: one on the Muralla Real, and another on the San José bastion, gathering information that helps explain their current state of conservation.