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. The spot was marked by a three-niched monument (aedicula) of 166–170 CE. (Excavations in 1940–49 revealed well-preserved catacombs, with both pagan and Christian graves dating from the period of St. Peter’s burial.) Constantine enclosed the aedicula within a shrine, and during the last 15 years of his life (c. 322–337) he built his basilica around it. The shrine was sheltered by a curved open canopy supported by four serpentine pillars that he brought from the Middle East. The design, enormously magnified, was followed in making the baldachin (1623–33) over today’s papal altar.

Other churches in Rome:

1. San Giovanni in Laterano
2. San Paolo Fuori le Mura (St. Paul Outside the Walls)
3. Santa Maria Maggiore