Perugino, Christ Giving the Keys of Heaven to St. Peter, a fresco in the Sistine Chapel
You can see The Domes of Rome 1 here.
You can see The Domes of Rome 2 here.
At the end of the 15th century, Rome was a wilderness of ruins. The city long ago contracted to less than a quarter of its original size. The remains of the ancient city of more than a million people formed a tangled maze of broken masonry and stone covered in wild vegetation. Crime and banditry thrived in the ruins and farmers herded cattle and sheep where senators once walked. Rome was a poor city despite its sanctity and the presence of the Pope. Most of the enormous ancient churches that generations of pilgrims traveled far and at great risk to see were crumbling and badly in need of repair. The south wall of St. Peter's faced imminent collapse. Last minute buttressing and temporary repairs prevented the worst from happening but didn't solve the problem.
The great city states of northern Italy, especially newly rich Florence, over-awed the crumbling splendors of a mostly ruined and uninhabited city with their new and magnificent cathedrals and palazzi publici. Those cities all boasted links to ancient Rome. The revival of Classical culture in the Renaissance gradually inspired the ambition to rebuild Rome as a world capital once again, but this time of an empire of souls in the Church. That ambition would expand as a succession of popes, artists, and architects engaged in two century long effort to build Rome anew.
In that ambitious rebuilding of Rome, the dome returned to the city that made such structures great and inspiring. The city of Florence topped their cathedral with a dome that surpassed in height and width the ancient Roman Pantheon. By the end of the 15th century, there was a determination to return such ambitious construction to the very city that inspired all of it.
Toward the end of the 15th century, Italian architects from Alberti to Leonardo da Vinci dreamed of domed centralized churches, taking their inspiration from the writings of Vitruvius whose books on architecture are the only writings of their kind to survive from Antiquity. Because of this association with Vitruvius, historians for a long time associated this shared vision of the church as a centralized domed building occupying the center of a broad open plaza as a kind of pagan revival. As Peter Murray points out in his book on Italian Renaissance architecture, this notion is mistaken. Most Roman temples were four square buildings occupying one end of a columned forum. There were some round temples, usually built for goddesses, especially Vesta. There are ancient Christian precedents for round churches, such Santo Stefano and especially Santa Costanza in Rome. Both of those buildings were martyria, built not for congregational worship, but for rituals of circumambulation around the tombs of martyr saints or other holy places.
These architectural visions of domed churches in central plazas for a long time appeared only in paintings such as the famous examples by Perugino and Raphael above. At the beginning of the 16th century, the architect Bramante finally built one, though small in size, in Rome. Bramante arrived in Rome from Milan in 1499, part of the exodus from Milan following the fall of its ruler Lodovico Sforza to the invading French. In 1502, he completed the Tempietto in a cloister of San Pietro in Montorio in the Trastevere neighborhood of Rome on a site revered by some as the site of St. Peter's crucifixion (the current consensus places the location of that event on the spina of the Circus of Nero on the south side of St, Peter's Basilica). This beautiful small building announced the advent of High Renaissance architecture and created a lasting influence on later generations of architects down to the present day.
The Tempietto was the gift of Ferdinand and Isabella of Spain to the monks of San Pietro in Montorio and to Rome.
The Tempietto in San Pietro in Montorio in Rome.
The architects of the Renaissance were indeed out to revive Classical culture and Classical art and design, but not necessarily to imitate it literally. They wanted to adapt it to the purposes of a new religion and a new era. Brunelleschi revived classical forms and proportions, adapting them to medieval design and construction methods. Alberti advocated a closer study of design and proportion emphasizing the monumental scale and volumetric aspect of ancient Roman architecture. Bramante in the Tempietto looking at the ruins of Roman monuments through through eyes instructed by Brunelleschi and Alberti revived that central idea in Classical design of completion. The building is whole and complete in the same way that our bodies are whole and complete. Nothing more may be added without distorting the design, and nothing large or small may be removed without mutilating it. Like us, it is whole and complete with all of its parts relating to each other in function and proportion resolving all into something as splendid and healthy as an athlete's body.
Temple of the Sibyl, Tivoli, 1st century BCE, possibly a temple to Vesta.
Bramante modeled the Tempietto after Roman round temples such as the Temple of the Sybil in nearby Tivoli. Like those temples, it is a masonry cylinder surrounded by a circular peristyle.
Even in the details, Bramante takes ancient Classical precedents and adapts them to the needs of the Christian religion.
The sumptuous interior of the chapel with paintings by Sebastiano del Piombo over the altar and on the walls and vaults by Francesco Salviati. The sculptures in the niches are Jonah by Lorenzetto who was Raphael's reliable in house sculptor, and Habakuk and the Angel by Bernini from about a century later.
The pyramidal tomb monuments to Agostino and Sigismondo Chigi were designed by Raphael and completed with modifications by Bernini.
Bernini's sculpture of Daniel waiting in the Lions' Den.
The dome mosaics are based on designs by Raphael and executed by Luigi di Pace in 1516. They show the Seven Planets under the divine influence of God the Father who appears in the oculus at the top of the dome.
Agostino Chigi took a keen interest in astrology. One of the painted ceilings in the pleasure palace he built for himself across the Tiber from Rome (now known as the Farnesina) may show his star chart as interpreted by the Sienese artist Baldassare Peruzzi. The mosaic cycle in the dome reflects those astrological interests and beliefs.
The oculus mosaic of God the Father.
Raphael's splendid drawing for God the Father, probably based on a model drawn from life in red chalk.
The mosaic of the planet Mars with a guiding angel in he dome.
Sant' Eligio degli Orefici
Raphael designed and built this church about the same time he was painting the great frescoes in the Stanza della Segnatura and is a sharp contrast to the later sumptuous Chigi Chapel.
Like the Chigi Chapel, this too was mostly left to others to build and complete such as Baldassare Peruzzi who probably designed the dome. The early 17th century facade was built by Flaminio Ponzio.