Here is a brief overview of the project's contents The Corpus Cosmatorum project is foundational art historical research (“Grundlagenforschung”). With its focus on the high and late medieval building history of Roman churches it complements and updates Richard Krautheimer's "Corpus Basilicarum Christianarum Romae" (5 vols., 1933–1977), which focused on the early Christian and early medieval period. This is not a history of art of the Roman Middle Ages based on its sacred buildings, rather one based on the careful recovery and reconstruction of their internal topography and layout, which, since the end of the 16th century, has been largely compromised. The polychromy of materials, the preference for precious marbles, and the splendor of golden mosaic tiles distinguished the aesthetics of medieval Roman sacred spaces from those common in Romanesque art throughout the rest of Europe. The revival of ancient architectural language and the reutilization of materials from Constantinian Rome appear to have been deliberately favored for the representation of the papacy at the height of its power. At the same time, the systematic study and reappraisal of individual churches represents an important contribution to the history of the sacred topography of the city of Rome during the Middle Ages. The short monographs of specific churches provide further information about the social groups influencing their architecture and decoration. In a society in which signs and visible distinctions were important, each church played a specific role in the tensions between the single political factions of Rome —the Papacy, the Curia, the Roman nobility, the Commune, and religious communities. And by reflecting on the reception and restoration of the churches up to the present day, these "building biographies" are part of our own intellectual history.