This book describes the geotechnical aspects for correcting the geometry of Mexico Citys Metropolitan Cathedral and of the adjoining Sagrario Church. It describes the main aspects of geotechnical conditions in the city and of the most important hazards affecting these monuments. It discusses the analyses performed and the actions taken to achieve the corrections required. The book aims to provide non-specialists with a clear picture of the magnitude and importance of the project and of the achievements it fulfilled. It is expected that the book will also appeal to specialized geotechnical engineers that will be provided with references to follow up the project in depth. The book will contain a large number of illustrations and will be written so as to provide "down to earth" explanations of the basic theories applied and of the actual construction procedures The work will appeal to both students and professionals in the fields of Architecture and Civil Engineering. It will also interest specialized audiences of geotechnical engineers and conservation architects and it may also be of value to art historians.