 The Cardinal Palace was enlarged by cardinal Stefano Conti, a nephew of Pope Innocent III.Cardinal Conti also transformed the palace into a fortress, to shelter Popes in the Lateran during the conflict with the Hohenstaufen emperors.In 1247, the chapel of St Sylvester, on the ground floor of the fortress, was consecrated; it contains frescoes depicting the stories of Pope Silvester I and Emperor Constantine I, among which the un-historical baptism of the emperor, as well as a depiction of the Donation of Constantine.