From Gregory to Bernini: The Evolution of Saint Peter’s Presbytery and the Living Legacy of the Apostle’s Tomb.
This is a short summary of my thesis on the presbytery of Pope Gregory the Great in the Constantinian basilica of St Peter in Rome. My fascination with this subject comes from both faith and place: I was born and raised in Rome, where the basilica of St Peter dominates not only the skyline but the imagination of anyone baptized here. Yet I am also Anglican, and thus spiritually linked to Gregory himself—the Roman pontiff who, in the late sixth century, sent Augustine of Canterbury to convert the Angles and lay the foundations of the Church of England. To study Gregory’s sanctuary, where he worshipped and where he now rests, is for me to explore the meeting point of Rome and Canterbury, of origin and inheritance, of the Church universal and my own faith tradition.
The first basilica of St Peter was commissioned by Emperor Constantine between about 326 and 333 CE, rising on the southern slope of the Vatican Hill directly above the apostle’s tomb. It was a vast, five-aisled Latin basilica built partly from reused Roman materials (spolia), aligned with the second-century trophaeum that marked Peter’s burial place. A great apse at the east end displayed a mosaic of Christ with Saints Peter and Paul, while a spacious quadriporticus—called the “Paradise”—stretched in front of the façade. Over time, this monumental church became the goal of Christian pilgrimage from across the empire.
By the late sixth century, however, the city of Rome had declined to perhaps 30,000 inhabitants. Ruined monuments were stripped for stone, the population was impoverished, and the Church had become the true caretaker of the city. Gregory the Great (r. 590–604), a former senator turned monk, diplomat, and bishop, inherited this wounded world. His writings—the Moralia, Dialogues, and Regula Pastoralis—and the early Ordines Romani reveal his conviction that the Eucharist was not a symbolic act but a real encounter between heaven and earth. For Gregory, the Mass united the living and the dead, the Church militant and triumphant, through the offering made “on the body” of the apostle himself. This theology demanded a transformation of the space around Peter’s tomb: the liturgy had to be both visible and accessible to pilgrims, yet centered on the altar of sacrifice.
Under Pelagius II and Gregory, therefore, the entire sanctuary of the Constantinian basilica was rebuilt. The floor of the presbytery was raised by roughly 4 feet 9 inches above the original level, forming a massive podium that incorporated the apostle’s tomb within it. Inside this structure ran a semi-annular crypt, about 5 feet 3 inches wide and 6 feet 10 inches high, where pilgrims could approach ad corpus by two side stairways. At the front opened a fenestella confessionis, a small window through which they could pray directly toward the tomb below the altar. On this new platform stood the high altar “over the body of the blessed Peter”, covered by a silver ciborium supported on four columns—traditionally described as porphyry, a symbol of imperial dignity, as reported by the Liber Pontificalis. The visual and theological axis was now unmistakable: tomb → altar → ciborium → apse, a vertical path joining earth and heaven.
The pergula, or chancel screen, defined the threshold between clergy and congregation. Along the front of the podium Gregory reused six twisted vine-scroll columns, the celebrated “Solomonic” columns taken from the Constantinian baldachin. Each stood about 5 feet high, carved with spiraling vines and grapes—an unmistakable symbol of the Eucharist. These were linked by an entablature from which hung lamps and silver chains, forming both a physical barrier and a luminous frame for the altar. Some of these ancient columns survive today in the modern basilica, set into the balconies near the high altar and the Chapel of the Blessed Sacrament, a tangible link to Gregory’s sixth-century design.
Access to the raised sanctuary was by twin stairways of eight to ten steps, leading up to a floor inlaid with marble revetment panels (crustae marmoreae). Gregory personally ordered this embellishment, writing that it was unworthy for the place of the divine mysteries to appear “bare or poor.” Behind the altar, centered in the apse, stood the papal throne (cathedra), flanked by benches for the presbyters. The arrangement created a unified liturgical geometry: the faithful in the nave, the clergy gathered around the altar, and the bishop of Rome presiding from his chair in direct line with the tomb of the Apostle. The Gospel was proclaimed from the ambo built by Pelagius II, and according to the Ordines Romani, the pope descended first to the confession to pray, then ascended the steps to celebrate Mass—an enactment of resurrection itself.
Archaeological excavations confirm the outline of Gregory’s crypt and confessio beneath the present basilica. While the original ciborium and podium no longer survive, their forms are securely known from written sources, drawings, and the later medieval replicas they inspired. Gregory’s reorganization of the sanctuary was not a matter of architecture alone; it was the spatial expression of his liturgical and theological reforms—the first great medieval reshaping of Christian worship.
For centuries the Gregorian sanctuary remained intact. In the twelfth century Pope Callistus II added a Romanesque altar and ciborium dedicated to Saints Processus and Martinian, still maintaining the same vertical alignment. Over time, however, the ancient structure weakened. By the fifteenth century the old Constantinian basilica was decaying, prompting Pope Nicholas V and later Julius II to plan an entirely new church. During this long transition, the original presbytery was enclosed and protected. Donato Bramante, architect of the Renaissance basilica begun in 1506, constructed a temporary wooden canopy known as the “tribuna” over the old altar to preserve worship at the tomb while demolition advanced. The sacred topography of Gregory’s sanctuary—its levels, steps, and the direct line from tomb to altar—guided Bramante’s and Michelangelo’s alignments for the new basilica’s crossing.
In the sixteenth century, Pope Paul III Farnese reinforced the presbytery area with new masonry walls as the old apse was dismantled, ensuring that the tomb remained undisturbed. During this period, the last surviving “Solomonic” columns were removed and carefully preserved; nine are now displayed within the modern church, revered as relics of the ancient shrine. Their twisting forms continued to symbolize both continuity and renewal.
The culmination came with Gian Lorenzo Bernini, who between 1624 and 1633 created the monumental bronze Baldacchino over the papal altar. Commissioned by Pope Urban VIII, it was cast from bronze taken (symbolically if not literally) from the Pantheon and gilded with gold. Its colossal spiral columns—each nearly 66 feet high—reimagined Gregory’s vine-scroll shafts on a cosmic scale, transforming the early Christian ciborium into a triumphal Baroque statement. The vertical line first articulated by Gregory—the tomb beneath, the altar above, the canopy rising toward the dome—was magnified into the defining symbol of St Peter’s itself. Bernini’s design united imperial Rome and Christian Rome, Constantine and Gregory, martyr and pope, in a single ascending axis that still structures the basilica today.
From Constantine’s builders to Bernini’s artisans, the presbytery of St Peter’s has embodied a continuous dialogue between architecture, theology, and devotion. Gregory the Great’s sixth-century vision—linking the Eucharist, the martyr’s tomb, and the pastoral authority of the bishop—remains visible in every later phase. The spiral columns of his pergula, echoed in Bernini’s bronze giants, still proclaim the same mystery: that at the altar above Peter’s grave, heaven and earth meet, and the living Church is united with the apostle whose faith became its rock.
