The paper presents a study carried out to restore Sultan Qalawun Mosque that was built in the Fatimids epoch. This magnificent monument was deteriorated structurally and architecturally. The most critical problem was due to differential settlement of the foundations as a result of severe environmental changes. Geotechnical and geophysical investigations were carried out. The masonry building was monitored for a period of time and structurally analyzed. Rehabilitation schemes included the execution of micro-piles to strengthen the foundations and the bearing soils. Repairs were carried out for all the damaged structural elements to restore this valuable historical monument.