In the collective memory of Western Christendom it is the basilica of St Peterߣs that is the mother church of Latin Christianity. However, this rank officially appertains to the Basilia of St John Lateran built by Constantine as the Cathedral of Rome. The fact that today the Lateran is no longer perceived as the Cathedral of Rome might go back to the 14th century, when the Popes returned from Avignon and re-established their Roman residence near the basilica of St Peter. But already as early as the sixth century Pope Symmachus (498-514) erected episcopia on both sides of the atrium of St. Peterߣs and copied the display of the Lateran baptistery with its three oratories in the baptistery of St. Peter. This was a highly symbolic act, directed against his opponent Laurentius, who was elected antipope in the very same year as Symmachus. In later centuries it was mostly in periods of conflict that the two basilicas – St John Lateran and St Peterߣs – assumed imporant roles as places of display of rival interests. This chapter investigates the visual strategies of these rival claims through its study of architecture, tombs, relics and images.