The richness of historical heritage and the complex stratification of sites, combined with the defensive functions and techniques of the fortifications, confer an added value to the cities overlooking the Mediterranean Sea. The fortifications and the new harbours of Tripoli, Libya and Alexandria, Egypt are not isolated structures, which just enhance the qualities and visibility of the places where they are built. Rather, as they come into contact with the pre-existing ancient urban systems, harbours and fortifications contribute to enriching the architectural qualities and values of the cities. In such situations, the new defensive interventions assume a strong transformational role in relation with the sites where they are located, and thus create new urban realities, and new meanings to be deciphered. In the discovery of these new interpretive possibilities, lies the fascination these studies can still offer today.