Only after the return of the Popes from their exile in Avignon in the year 1377, did the Vatican become the centre of the Catholic Church. It replaced thereby the old seat of the Popes in the Lateran. The first building of St. Peter goes back to the Emperor Constantine, who erected the church over the tomb of the apostle Peter. In 1506 Pope Julius II laid the first stone of a new church. It took more than a century to build, and all the great architects of the Roman Renaissance and Baroque period had a hand in its design. Amongst them were: Michelangelo, Raphael, Bramante, Bernini and Borromini. Since 1277 a secret corridor has lead from the Vatican Palace to Castel Sant’Angelo that takes its name from the statue of the Archangel Michael on its summit. The monument is of great interest because of the different functions it has had during the centuries. Originally it was a mausoleum for the Emperor Hadrian; then it became a part of the Aurelian city wall; it was a medieval citadel and prison and lastly, the residence of the Popes in times of political unrest. The history of the castle, its beautiful wall paintings inside and the amazing view from the terrace on the top, make it one of the most interesting buildings in Rome!