symbols (angel, lion, ox and eagle) are the oldest still existing such representations of the Evangelists. The backdrop is a blue sky with an orange sunset. One scholar has suggested that the enthroned figure in the center of the apse mosaic normally regarded as Christ, in fact represents God the Father, which would be an extremely unusual depiction of God the Father in art at this date. Chapels The Peter chapel, on the left side of the apse, contains a part of the table at which Peter the Apostle would have held the celebration of the Eucharist in the house of Pudens. The rest of the table is embedded in the papal altar of St. John Lateran. The sculpture on the altar depicts Christ delivering the keys of Heaven to St. Peter (1594) by the architect and sculptor Giacomo della Porta. In the same chapel there are two bronze slabs in the wall, explaining that here Peter was given hospitality and that Peter offered for the first time in Rome bread and wine as a consecration of the Eucharist. The pavement is ancient. A door opens into a cortile with a small chapel that contains frescoes from the 11th century. Chapel of the Crucifix: contains a bronze crucifix by Achille Tamburini. Chapel of the Madonna of Mercy: contains the painting The Nativity of the Madonna by Lazarro Baldi Chapel of St. Bernard: contains a painting of St Benedict and St Catherine of Siena Caetani chapel: This chapel for Caetani family (family of Pope Boniface VIII) was designed by Capriano da Volterra in 1588 and, after his death in 1601, completed by Carlo Maderno. The mosaics on the floor are notable. The columns of Lumachella marble. The relief (1599) above the altar is by Pier Paolo Olivieri and depicts Adoration of the Magi. Giovanni Paolo Rossetti painted St Praxedes and Pudenziana collecting the Blood of the Martyrs in 1621. He also painted the fresco of the Evangelist in the ceiling, to a design by Federico Zuccari. The statue of Saint Pudentiana (c. 1650) in a niche is by Claude Adam. The sisters’ well stands just outside the Caetani chapel in the left aisle, which is said to contain the relics of 3,000 early martyrs, many of which were brought here and hidden by Pudentiana and Praxedes. This is marked by a square porphyry slab in the floor. Following the decline of