Geography and Topography
Rome sat on a defensible hill that dominated the last downstream, high-banked river crossing where traverse of the Tiber was facilitated by a midstream island. This hill, Palatine Hill , was one of a group of hills, traditionally counted as seven, around which the ancient city grew. Some 25 of the original parish churches, or tituli , the first legal churches in Rome, still function. Most had been private houses in which the Christians illegally congregated, and some of these houses, as at Santi Giovanni e Paolo, are still preserved underneath the present church buildings. Since the 4th century the tituli priests have been cardinals who, over the centuries, have rebuilt, enlarged, and embellished their churches. Protected by the fortified Castel Sant’Angelo, St. Peter’s Basilica was built over the traditional burial place of the apostle Peter, from whom all popes claim succession....