St Peter's Basilica in Rome

The largest church in Christendom

St Peter's is, by interior surface, the largest church in the world.^[1] Its interior length reaches nearly 187 metres; with the portico, the building is about 220 metres long. Its interior surface of about 15,160 m²^[2] can hold more than 60,000 people.^[3] The nave floor bears, inlaid in marble, the lengths of the world's largest churches, all shorter: an eloquent way of reminding visitors of the extraordinary scale of the place.

These dimensions are not a matter of technical prowess alone. Decided by Julius II in 1506 — thus before the Protestant Reformation — to replace a millennial basilica threatening ruin, the rebuilding then took on, with the Catholic Reformation that followed the Council of Trent, the meaning of a visible affirmation: the Church was building, over Peter's tomb, the greatest temple ever raised to the living God. The excess of the building is an argument in stone.^[4]

The tomb of the apostle Peter, the reason for the building

Everything in this basilica is ordered to a single point: the tomb of St Peter. It is not the basilica that chose its site for reasons of convenience; it is the tomb that has fixed, since the 4th century, the exact centre of the building. The high altar, Bernini's baldacchino, Michelangelo's dome: all rise on the vertical line of the apostle's grave.^[5]

“And I tell you, you are Peter, and on this rock I will build my Church, and the powers of death shall not prevail against it.” — Gospel according to St Matthew 16:18^[6]

This word of Christ, inscribed in giant letters all around the base of the dome, is no decoration: it is the key to reading the whole building. The basilica says in stone what the Gospel says in words — that the Church is built on Peter, and that Peter's successor dwells here.

A major basilica, but not the pope's cathedral

It must be said again, for the confusion is universal: St Peter's is not the cathedral of Rome. A diocese's cathedral is the church that houses the cathedra, the bishop's seat; and the Bishop of Rome is the pope, whose cathedra stands at St John Lateran, “mother and head of all the churches of the City and of the world”.^[7]

St Peter's holds its rank from another dignity: it is one of the four major basilicas of Rome — with the Lateran, St Paul Outside the Walls and St Mary Major — and the most illustrious by its apostolic tomb, its size and its function in the pontifical liturgy. The following table places St Peter's among these great Roman sanctuaries.

From Constantine to Julius II: a thousand years of the first basilica

The present basilica had a predecessor. Around 323, Emperor Constantine had raised, on the flank of Vatican Hill, an immense five-aisled basilica whose apse enclosed the “trophy” — the small funerary monument that had marked Peter's tomb since the 2nd century.^[8] Dedicated according to tradition in 326, it was completed after Constantine's death.^[9] The project was a challenge: to respect the exact site of the grave, part of the hill had to be levelled and a pagan necropolis filled in, instead of building on flatter, more convenient ground. The full story of this foundation is treated in the article The building of the old St Peter's Basilica.

For twelve centuries, this Constantinian basilica was the heart of Western pilgrimage. It was there that Charlemagne was crowned emperor at Christmas 800. But by the 15th century, the millennial building was leaning, cracked, threatening to collapse.

The present basilica (1506–1626)

On 18 April 1506, Pope Julius II laid the foundation stone of an entirely new basilica, making the radical decision to raze Constantine's venerable basilica. The works stretched over 120 years and passed through the hands of the greatest: Bramante designed a Greek cross; Raphael returned to the Latin cross; Michelangelo, appointed architect in 1547 at seventy-two, designed the dome; Carlo Maderno lengthened the nave and built the facade (1607–1614); Bernini crowned the work with the baldacchino, the square and the Chair.^[10] The solemn consecration took place on 18 November 1626 by Pope Urban VIII.

The whole history of this building site — the successive architects, the funding through indulgences that triggered Luther's reaction, the architectural choices — is told in the article The building of the present St Peter's Basilica. The timeline below keeps only its milestones.

The dimensions of a colossus

A few figures give the measure of the building.^[11][12]

The dome of St Peter's remains the tallest dome in the world.^[13] Its diameter is still slightly smaller than that of the Pantheon in Rome or Santa Maria del Fiore in Florence; but none of those domes reaches its height.

Bernini's colonnade: “the arms of the Church”

Before even entering, pilgrims are seized by St Peter's Square, the vast ellipse drawn by Bernini from 1656 to 1667 for Pope Alexander VII. Two arms of colonnade — 284 Doric columns in four rows, crowned by 140 statues of saints — embrace the crowd.^[14] The meaning Bernini himself gave to his gesture is reported by his biographer: St Peter's being as it were the matrix of all churches, its colonnade had to open maternal arms to welcome Catholics and confirm them in their faith, bring heretics back to unity and enlighten unbelievers with the true faith.^[15]

The Vatican obelisk, a silent witness

At the centre of the square stands an Egyptian obelisk of red granite, 25.3 metres high (nearly 40 metres with pedestal and cross).^[16] Without hieroglyphs, it was brought from Heliopolis to Rome by Emperor Caligula and raised at the heart of Nero's circus, on Vatican Hill.

That is its whole spiritual weight: this monolith is the only great material witness still standing of the place where, according to tradition, Peter was crucified under Nero, around the year 64. The obelisk “saw” the apostle's martyrdom. Left standing amid the ruins of the circus for fifteen centuries, it was moved to its present site by the engineer Domenico Fontana, on the orders of Pope Sixtus V — a feat of which Fontana left a detailed account (Della Trasportatione dell'obelisco vaticano, Rome, 1590): for the final raising on 10 September 1586, some nine hundred men and seventy-five horses worked about forty winches.^[17] At its top, Sixtus V had the bronze cross placed that crowns it, thus Christianizing the pagan monument: the sign of Christ now crowns the stone that witnessed the death of his apostle. A tradition also sees there the deposit of a fragment of the True Cross; that deposit is not established.^[18]

Maderno's facade and the Benediction Loggia

The facade, the work of Carlo Maderno (1607–1614), stretches some 115 metres wide and 45 metres high.^[19] At its centre opens the Benediction Loggia: from this balcony the election of a new pope is proclaimed — “Habemus papam” — and the sovereign pontiff gives the Urbi et Orbi blessing, “to the City and to the world”, on the great feasts. The facade was criticized for its width, which partly hides the dome as one approaches; but seen from the far end of the square, the whole recovers its majestic balance.

The Confessio and Bernini's baldacchino

At the crossing of the basilica, beneath the dome, opens the Confessio: an open crypt, ringed by a balustrade where lamps burn perpetually, descending toward the apostle's tomb. It is the geographical and spiritual heart of the building.

Above rises Bernini's baldacchino — commissioned by Urban VIII in 1624, executed from 1624 to 1633^[20] — a monument of gilt bronze nearly 29 metres high — the equivalent of a nine-storey building — carried by four twisted columns recalling the Solomonic columns of the old basilica. It marks and shelters the papal high altar, on the exact vertical line of Peter's grave. The bronze, according to a tenacious tradition, was partly taken from the portico of the Pantheon, which inspired the sharp saying: “What the barbarians did not do, the Barberini did”, a play on the name of Pope Urban VIII Barberini.^[21]

The excavations and the apostle's bones

What do we really know about Peter's tomb? In the 20th century, the Church wanted to know for certain. From 1939 to 1949, Pope Pius XII had excavations undertaken beneath the Confessio, which uncovered an intact Roman necropolis and, at its centre, the “Trophy of Gaius”, the 2nd-century funerary monument venerated as Peter's grave.^[22] The archaeologist Margherita Guarducci deciphered there the Greek graffito “Petros eni” — “Peter is here”. On 23 December 1950, Pius XII announced that the apostle's tomb had been found; in 1968, Paul VI declared that bones identified with serious probability were those of Peter.^[23] The full archaeological dossier is treated in the article on the old basilica.

The papal high altar

At the altar raised beneath the baldacchino — called the “papal altar” — only the pope celebrates Mass, except by express authorization: this is the basilica's own usage, attested from early times and maintained today by the Chapter of St Peter's — a usage analogous to that of the Lateran papal altar.^[24] This altar, consecrated by Clement VIII in 1594, encloses within its structure the older altars of Callixtus II (1123) and Gregory the Great (c. 600), themselves raised over the 2nd-century trophy: a superposition of fifteen centuries of veneration in a single spot.^[25]

Michelangelo's Pietà

In the first chapel of the right aisle, visitors meet one of the summits of Western sculpture: Michelangelo's Pietà (1498–1499). The young artist — barely twenty-four — shows the Virgin holding on her knees the body of the dead Christ, in a composition of overwhelming gentleness and mastery. It is the only work Michelangelo ever signed: his name can be read on the sash across the Virgin's breast, a gesture he is said to have regretted as a movement of pride. Since the 1972 hammer attack by a disturbed man, the statue has been protected behind bulletproof glass.^[26]

The Chair of St Peter (Cathedra Petri)

At the far end of the apse, closing the nave's perspective, Bernini raised his Cathedra Petri — begun in 1657 and completed in 1666 —: a monumental bronze throne encasing an ancient seat venerated as the chair of the apostle Peter. Four Fathers of the Church — Ambrose, Augustine, Athanasius, John Chrysostom — support the throne, while above radiates a glory of gilt stucco, pierced by an alabaster stained-glass window depicting the dove of the Holy Spirit. The whole proclaims one idea: Peter's chair, that is the pope's magisterium, is carried by the tradition of the Fathers and enlightened by the Holy Spirit.^[27]

The bronze statue of St Peter and the worn foot

Against one of the nave pillars stands a bronze statue of St Peter seated, right hand raised in blessing, left hand holding the keys. Attributed by tradition to Arnolfo di Cambio (13th century), it is the object of unbroken devotion: for centuries, pilgrims have kissed or touched the apostle's right foot, so much so that the bronze is now polished and thinned, the toes almost worn away.^[28] This foot, worn by millions of hands, is perhaps the most telling image of what St Peter's is: not a museum, but a living place of prayer.

Michelangelo's dome and the “Tu es Petrus”

Raising one's eyes beneath the dome, one meets, running all around the drum in letters of blue on gold nearly two metres high, the founding verse:

“YOU ARE PETER, AND ON THIS ROCK I WILL BUILD MY CHURCH — AND I WILL GIVE YOU THE KEYS OF THE KINGDOM OF HEAVEN.” — Inscription on the dome drum, after Matthew 16:18–19^[29]

The dome, designed by Michelangelo and closed after his death by Giacomo della Porta and Domenico Fontana in 1590 — the orb and cross crowning it being set in 1593 — rises to more than 136 metres.^[30] From inside, its gilt coffers and mosaics draw the gaze toward the lantern, inscribed with the dedication: “To the glory of St Peter, Sixtus V, pope, in the year 1590”. Pilgrims climbing its steps emerge onto one of the most famous views of Rome, overlooking the square and the city.

Beneath the basilica floor stretch the Vatican Grottoes, laid out at the level of the old Constantinian basilica. This is the necropolis of the popes: many sovereign pontiffs buried at St Peter's rest there, from the earliest centuries to contemporary popes.

Popular devotion focuses today on two tombs in distinct places: that of St John Paul II (died 2005, canonized 2014), first placed in the Grottoes then transferred in 2011 to the St Sebastian chapel of the upper basilica, and that of Benedict XVI (died 2022), buried in the Grottoes. The popes buried at St Peter's are carried there at the end of funerals most often celebrated on the parvis and square, before immense crowds and the whole world — a rite recalling that St Peter's is not only a sanctuary of the past, but the place where, generation after generation, the living history of the papacy is written.^[31]

The great pontifical celebrations

St Peter's is the par excellence stage of the pope's liturgy. Christmas Midnight Mass, Easter Vigil, Chrism Mass, ordinations, consistories: the most solemn celebrations of the Church unfold here. The basilica (more than 60,000 people) and the square extending it (about 300,000 people) can gather, together, several hundred thousand faithful.^[32]

Canonizations

It is on the parvis of St Peter's that the new saints have been proclaimed for centuries. The formula of canonization, pronounced by the pope, solemnly inscribes a servant of God in the catalogue of saints. Great crowds press there for figures such as Padre Pio, Mother Teresa, John XXIII or John Paul II — each canonization recalling that the basilica of the first of Rome's saints is also the place where the Church recognizes its most recent saints.

The Holy Door and the jubilees

In the basilica's portico opens the Holy Door, walled up most of the time, which the pope unseals and crosses first to open a jubilee year — every twenty-five years in ordinary course, or during extraordinary jubilees. Crossing this door is, for pilgrims, the sign of passing through Christ, “the door of the sheep” (John 10:7); but that passage alone is not enough to obtain the jubilee indulgence: it requires the usual spiritual and sacramental dispositions — detachment from all sin, confession, communion, prayer for the pope's intentions — joined to the accomplishment of the prescribed act, and it may also be obtained through the other ways provided by the norms (pilgrimage to other designated places, pious visits, works of mercy and penance).^[33] The Jubilee of 2025 — proclaimed by the bull Spes non confundit on the theme “Pilgrims of Hope” — once again opened that door to millions of pilgrims.^[34]

The council and authority

St Peter's has also framed decisive moments in the Church's government: it was in the basilica that the two Vatican councils were held — Vatican I (1869–1870), gathered in the transept, which defined pontifical infallibility, and Vatican II (1962–1965), gathered in the nave, the largest episcopal assembly in history.^[35] The place is not incidental: it is over Peter's tomb that the Church, gathered around his successor, restated and deepened its faith.

A stone for the Rock

Why so much marble, bronze and gold around a simple grave? Because this tomb is not that of just any man, but of the one Christ established as the visible foundation of his Church. The whole basilica is a catechesis in stone on Peter's primacy: it translates into space what faith confesses.

“Come to him, to that living stone, rejected by men but in God's sight chosen and precious; and like living stones be yourselves built into a spiritual house.” — First Letter of St Peter 2:4–5^[36]

The words are Peter's own. The apostle whose body rests beneath the high altar taught that the true Temple is not made of dead stones, but of living souls gathered upon Christ. The gigantic basilica covering him is thus only a sign: the true house of God is the people of the baptized, whose unity Peter and his successors secure.

The goal of a seventeen-century pilgrimage

Since the 2nd century, Christians have come to pray on this precise spot of Vatican Hill. Before the basilicas, before the Christian emperors, they already came to gather before the modest trophy marking the grave. The basilica of Constantine, then that of Julius II and Bernini, only wrapped in ever more splendour this humble and constant gesture: coming to pray near Peter.

That is what keeps St Peter's from being a museum. A visitor may see in it only the greatest masterpiece of Western architecture; believers recognize the place where, since the basilica of Constantine — seventeen centuries ago —, the Church stands beside its first shepherd, confessing that “the gates of hell shall not prevail” against the spiritual edifice built on the Rock.

• The building of the old St Peter's Basilica — the first Constantinian basilica (begun c. 323) and the archaeology of Peter's tomb.
• The building of the present St Peter's Basilica (1506–1626) — Bramante, Michelangelo, Bernini and the 120-year building site.
• St John Lateran Basilica — the pope's true cathedral, “mother of all churches”.
• St Paul Outside the Walls Basilica — Rome's other great apostolic basilica, over Paul's tomb.
• St Mary Major Basilica — the fourth major basilica, Rome's largest Marian church.
• The Sistine Chapel — the chapel of the conclaves where the pope who reigns over St Peter's is elected.