ABSTRACT: In this paper we describe the project for the geometrical correction of Mexico City’s Metropolitan Cathedral and Sagrario Church. In the first part of the project both temples were underexcavated between 1993 and 1998. The corrective deformations induced by this procedure nullified most of the differential settlement that accumulated during the previous 65 years, due to regional subsidence. Upon the end of underexcavation, the effects of regional subsidence reappeared and some of the corrections gained were lost. We also describe the second part of the in which the very soft clayey soils underlying the Cathedral and the adjacent Sagrario Church were hardened selectively by means of injected mortars, as a preventive measure to avoid the accumulation of future differential settlements. Observational data demonstrate that the procedure has been successful.