In an alphabetic catalogue the volume lists the Roman churches described in the most important medieval guide for pilgrims to Rome, the »Indulgentiae ecclesiarum orbis Romae«, a source hitherto remarkably neglected by historical research. The list begins with the 7 main churches in Rome, followed by some 170 further places of worship. In each case the information found in the medieval sources is grouped under different headings (e.g. Relics, Indulgences, Interiors/Features). The catalogue thus provides a swift overview of the knowledge available in the late Middle Ages about Rome's churches and their characteristic features.