<p>This paper investigates the provenance and characteristics of building limestones from the Casbah of Algiers in the context of its restoration. Petrographic and petrophysical analyses of samples from traditional houses built during the Ottoman period and later modified under French rule, combined with geological fieldwork and GIS mapping, identified three distinct varieties from Upper Pliocene outcrops surrounding the city. These include a compact rhodalgal limestone employed for refined architectonic elements, a softer sandy limestone used in masonry, and a pale brown calcarenite applied in refurbishment works. The study also established a correlation between the material properties, building functions and quarrying fronts, revealing a constructive logic and selective use of limestones. Beyond their technical significance, these findings highlight the deep interrelation between urban geology and built heritage, demonstrating how knowledge of historical stone supply contributes to the preservation of traditional building practices, the sustainable management of heritage sites, and the safeguarding of quarrying landscapes as key components of authenticity and cultural heritage.</p>