Through the visit of the four basilicas of Rome you can get into the heart of Christianity. S. Peter, the largest basilica in the world was founded on the tomb of Peter and has since been the burial place of many Popes. St. John Lateran, the cathedral of Rome, adorned with the works of Borromini. Santa Mary Major, famous for its mosaics. St. Paul outside the Walls: founded  on the grave of St. Paul.