Crucifixion of St Peter

The painting is a predella panel on the Pisa Altarpiece. St. Peter’s crucifixion presented difficulties for artists because, to avoid irreverent comparison with Christ, he insisted on being crucified upside down. Peter was in Rome, but his followers urged him to flee before he could be killed. As he was leaving Rome he encountered Jesus in a dream. Jesus was walking towards Rome and Peter asked, “Quo Vadis?” (where are you going?). "To Rome to be crucified again" Jesus replied. Peter was so ashamed of himself that he returned to Rome to die a Martyr’s death.