The main facade of San Giovanni in Laterano (St. John in Lateran) with the adjoining Lateran Palace. Built during the reign of Emperor Constantine the Great, and rennovated many times over the centuries, San Giovanni is the "Mother Church" in Christian history, and is the first of the four major Basilicas of Rome. The Lateran Palace was the Papal residence for close to 1500 years and was the "Vatican" of the Middle Ages. The basilica still remains today the Pope's titular church, and along with St. Peter's, St. Mary Major and St. Paul outside the Wall contains a "Porta Santa" (Holy Door) which is openned by the Pope to inaugurate a Holy Year. Click  INTERIOR to view the knave and Papal altar.