To experience what it felt like to enter one of the vast civic basilicas of ancient Rome, you must visit St. Paul Outside the Walls. There can be no doubt that it is one of Rome's greatest and most impressive churches. It is second in size only to St. Peter's, and its architecture and style of decoration would be familiar to any ancient Roman. Enter through the "Holy Door" (only available during Jubilee years), and you look down a huge space with a forest of granite pillars. It takes a few seconds to realize that you are only seeing one of the smaller side aisles of this grand five-aisled basilica. The colors are brighter, the architectural details are sharper, the grime of years of candle-wax, dust, and pilgrims' sweat has been cleaned away, and everything looks newer than what you can see in the other great Roman churches. And therein lies the problem: St. Paul's is only 150 years old, and it has neither the wear and tear of antiquity nor the Baroque overlays that art and architecture critics in Rome love so well. It is "new", and therefore undervalued, like the portrait of Sir Roderic, which comes to life in Gilbert and Sullivan's operetta, Rudigore.--- "I am crude in color, but I've only been painted ten years. In a couple of centuries I shall be an old master, and then you'll be sorry you spoke lightly of me." ---Ghost of Sir Roderic Murgetroyd
Unlike most similar "locations" in Rome, there is an unbroken tradition attesting to the validity of the situation of this church. It covers the spot where Paul was buried in the vineyard of a pious Christian woman. From the time of Paul's funeral, the site was revered, first with an often-visited above-ground funerary monument (called a "trophy") and then by Constantine's church, which was dedicated by the first Pope Sylvester in 324. But Constantine's church was not big enough hold the crowds of Christians who thronged to the tomb, and within 150 years a much more grand basilica had replaced it.
Some sources say that the new church, which had the same form that we see today, was called the "basilica of the three emperors", because it was funded by Valentinian II, Theodosius, and Arcadius, but that all may be a misunderstanding of the name Basilica Trium Dominorum, which the church acquired in its fifth century rededication, when two Ostian martyrs were added to Saint Paul in its name. But the Ostians were soon forgotten, and, over the centuries, emperors, popes, kings, nobles, and other plutocrats contributed to the decoration and expansion of the basilica in the name of Paul. There were barbarian depredations -- both the Longobards (739) and Saracens (847) carried off treasures -- but the fabric of the church survived, and later donors replaced the losses. Eventually St. Paul's church and its surroundings had to be heavily walled and fortified, just as St. Peter's was a few year earlier: both churches were "extra muros" (outside the city walls of Aurelian) and on the banks of the Tiber where undefended sites were easy prey for water-born raids.
From then on, the basilica continued to accumulate artistic and architectural treasures -- the mosaics, paintings, and frescoes, the great ciborium and tabernacle, the gold-plated doors (restored and visible as the Holy Door today), the great Paschal candelabrum, the splendid medieval cloister -- until it was the biggest and richest church in the world, far surpassing even St. Peter's in the Vatican. St. Peters, in fact, crumbled while St. Paul's grew. It was only when "new" St. Peter's was eventually built in the Baroque style (1506-1626) to replace Constantine's dilapidated structure in the Vatican, that St. Peter's became the largest church in Christendom: even then it was only slightly larger that St. Paul's.
On the night of July 15, 1823, a disastrous fire, caused, it was said, by an overturned pot of roofers' lead, brought down most of the old basilica. The people of Rome flocked to the scene, but there was nothing to be done: the church was ruined. Pope Pius VII, already on his deathbed, was never told what had happened, and the burden of reconstruction fell to his successor, Leo XII.
In the Roman fashion, factions quickly formed in a months-long debate on how to rebuild -- should an entirely new design be used, or should the old plan be followed. Eventually the group favoring reconstruction on the plan of the old basilica won out, and work began. New arguments quickly sprung up about how much of the old decorations could be saved and about whether saved art should be incorporated into the new fabric of the basilica.
Donations in cash and in materials streamed in from around the world as workers sought to replace what many people thought was forever lost. (Among the donations were the two new transept altars of precious malachite stone from the Russian Tsar and the great pillars inside the front entrance from the Turkish Sultan.) In the rebuilding, many early works of art were deemed unsaveable or simply passe, and they were destroyed, displayed in the small museum, or relegated to storage. Those who valued the old more than the new were then and still continue to be outraged. Reconstruction was completed by the mid-1850's. Certainly some of the best artists and artisans of the nineteenth century world participated in the refabrication, and what was saved, renewed, and replaced resulted in the harmonious and grand structure that stands today. In a few centuries, St. Paul's will certainly be considered and "old master." And if you must have the ancient today, visit the cloister and adjoining Benedictine monastery or see the two chapels flanking the main altar which escaped destruction in the 1823 blaze.
The Church and the monastery are on the Viale S. Paulo about one and a half miles outside Rome's Porta S. Paolo (old Porta Ostiensis, with the Pyramid of Cestius). St. Paul's has extraterritoriality and is part of the Vatican state.
It's worth the effort to read ahead before you visit St. Paul's -- otherwise you are likely to miss a lot. Good general guidebooks will give you some of the history and elucidate the important art in the basilica -- although some carp about what was lost or decisions made 150 years ago about what might be reused. Bookstores in Rome and online booksellers offer studies of the church that are more specific, ranging from short monographs to multi-volume sets.
The basics and a few pictures are available on the Internet, but that obviously does not compare with a site visit.
Bio of St. Paul: http://www.newadvent.org/cathen/11567b.htm
Porta S. Paolo: http://members.tripod.com/romeartlover/Vasi11.html
Captioned photos of the church, cloister and exterior of monastery: http://members.nbci.com/_XMCM/romeartlover/Vasi100.htm
Brief account of the highlights (scroll down): http://www.adoremus.org/6-72K.Gribben.html
Highlights in Italian: http://www.cicero.it/it/monumenti/chiese/SPaoFMu.htm