The fortress-churches of Maguelone, Agde, and Saint-Pons-de-Thomières were integrally involved in the political, social, and religious developments of mid-twelfth-century Languedoc. As three of the major cathedral and abbey churches of the region, they attracted important patrons and resident clergy, hosted kings and popes as visitors, amassed great wealth and prestige, and commissioned impressive architectural complexes. Though other churches and abbeys in the region may have shared their importance and their military aspects, the survival at these three great churches of both documentary and physical evidence of their mid-twelfth-century phases permits a fuller analysis than is possible for other buildings. We will focus in this chapter on a full “reading” of the fabric of each building as well as of the relevant archival sources for each community. In this endeavor we will make frequent reference to primary material. Resumés of the building histories of Maguelone, Agde, and Saint-Pons, from their foundation to the twentieth century, precede the more detailed analysis of the twelfth-century phases of each building. In this regard, we will discuss in detail the observations recorded in the new surveyed plans, measured elevations, and analytic section drawings produced for this book. The most important texts have been assembled in the Appendixes in both the original Latin as well as in new English translations. Identification of the twelfth-century phases of Maguelone, Agde, and Saint-Pons is only possible through detailed analysis of the buildings, careful reading of the archival sources, and critical reevaluation of the secondary sources.