The first mention of the presence of the Ark of the Covenant at the Lateran Cathedral in Rome was in a description of the cathedral from the early twelfth century, later labelled Descriptio Lateranensis Ecclesia (DLE), where it was said to be inside or beneath the church's high altar. This book asks how this claim in the DLE, that the spoils of the Jerusalem Temple rested in the Lateran, was understood and voiced within the context of the sacral topography of Rome and Western Christendom. It further explores the function of religious identities and the diverse and complex strategies for legitimizing sacerdotal authority during the age of reform and the Crusades. The book gives a presentation of the Descriptio and its transmission, as well as an edition and translation of one of the versions of the text (in an appendix).