The history of the tomb of the Apostle Peter at the Vatican has been enriched during the last thirty-five years since Pius XII, who at the very beginning of his pontificate, decided to extend archaeological investigations throughout the entire lower sections of the Vatican crypts and also under the papal altar. These investigations had been begun by chance at the site chosen for the burial of his predecessor, Pius XI.

Little by little, as the encrusted legends and learned theories were stripped away, the Memoria of Peter began to reappear in a more exact light, thus making possible a comparison of the monuments with ancient texts. This is the history we would like to relate, starting with the present Basilica and going back through the course of the centuries to the Basilica of Constantine, to the ancient 2nd-century necropolis and the small burial monument marking the site of Peter's tomb, and finally to the archaeological setting of the 1st century which offers a starting point.

The paradoxical character of this history stems from the fact that the small burial monument which, since the middle of the 2nd century, has never ceased to be the evidence on which this history is based, has stayed in place, despite successive raisings of the level of the ground, both in the first Basilica, built during the pontificate of Sylvester and the reign of Constantine, probably between 320 and 333, and in the present Basilica as well, built under eighteen popes from Julius II to Paul V, from 1506 to 1615. But, as is often the case, the contradiction is only an apparent one, as we shall see. The presence of the tomb has never ceased throughout the centuries to be the center of this history and its only justification.

This presence is that of a small burial monument built in the 2nd-centuty necropolis. It is made up of two superimposed niches forming part of a wall seven metres long. The niches were made in the middle of the wall at the time of its construction, about the year 150. Originally a marble plaque supported by two small columns separated the two niches. In front of this small monument there was an enclosure measuring seven metres by four. Some family monuments of the necropolis bordered part of it. That was how Peter's tomb appeared in the middle of the second century. It is easy enough to locate this modest set of constructions in the present Basilica. In fact, at the side of the small chapel called the Niche of the Palliums, under the papal altar, the small monument with niches and small columns has been discovered substantially intact, while some remains of the enclosure were discovered during excavations directly underneath the open area called the Confession which, protected by a balustrade, gives access to the Niche of the Palliums.

The tomb's first architectural setting, moreover, is now right before the eyes of visitors who descend from the Basilica into the crypts and pass through the archaeological area below those just mentioned. Thus taken suddenly from the present era into the 2nd century, the visitor walks along narrow paths hemmed in by the high family burial chambers of an ancient Roman necropolis. Having recovered from the surprise, the visitor realizes that he is walking on what was the slope of a hill. After a short climb to the north, he finds himself on the narrow main path which rises gradually towards the west in the direction of the papal altar, following the principal axis of the Basilica. As he moves on, the visitor gradually realizes that the family monuments he is passing have been demolished, more and more extensively, so that where the path ends, immediately under the papal altar, the last of the monuments consists only of a pavement and part of a wall.

Such a visit enables the visitor to form a good idea of the problems facing the architects of Constantine's time who were given the task of constructing the first Vatican Basilica. On the side of a hill where an important necropolis was located and which at that time was still being used, they managed to create an artificial plateau, by building imposing walls of substructure and by filling in the area with earth. The plateau was extended considerably beyond the site of the future Basilica. The level of the plateau was planned in such a way as to keep the small monument with niches intact and isolated at the focal point of the new structure, located directly in front of the apse. A simple burial monument in a necropolis, now closed by imperial authority, thus became the reason for the construction of a Basilica and the transformation of an entire area of what was then open country. Placed in the contemporary context of the martyria-basilicas, the way in which the Vatican Basilica was constructed is explained solely by the fact that the monument with niches was considered by the Christian community of Rome to be Peter's tomb. And without a doubt the most important result of the Vatican excavations is that it has been possible to recognize even in terms of the construction of the first Vatican Basilica the archaeological and historical proof for a community belief which was beyond dispute: if it is a palaeo-Christian Basilica built ad corpus, that is, to serve as a martyr's tomb, then it is clearly the one built at the Vatican according to Constantine's wishes.

Significant in the construction of the Basilica, the small monument is no less unusual in the 2nd century necropolis. In the first place, it is an individual building constructed in the middle of a large number of family monuments. Furthermore, it also interrupts the straight line which the others follow. In fact, the closest monuments are built around the enclosure with the small building in the center, as if it were an obstacle. Moreover, among these buildings two contemporary staircases were put in to provide access to the revered enclosure. Finally, the soil of the enclosure seems to be partly a built-up mound resting against the family monuments. The height of the mound is dictated by the height of the small monument built at a particularly steep point on the slope.

In the midst of these family monuments, therefore, the enclosure and the small building seem to answer to the desire that an already existing tomb should be preserved and integrated within the new necropolis then being developed. During the second half of the 3rd century, other plans attest to an identical wish. Two marble decorations and small walls were added to the small building, flanking it on each side. At the same time, the earth of the enclosure where, in the meantime, numerous ground burials had taken place, was covered over with a mosaic pavement. In addition, the paths to the two stairways were closed by gates.

An archaeological continuity is thus attested to, from the middle of the 2nd century when the small building was constructed up to the beginning of the 4th century which marks the start of the Basilica's construction: the Petrine identity of the small building at the beginning of the 4th century can thus be traced back historically to the middle of the 2nd century. The Vatican excavations have once again placed before our eyes the tomb as it was marked by the small building with niches before the construction of the Basilica.

These excavations have also allowed us to have a more precise idea of what visitors to the first Basilica saw, for they clarify and confirm the descriptions given by ancient texts and by a reliquary of the 5th century found at Samagher and now preserved in Venice. Isolated from the razed monuments and walls of the necropolis, the small Petrine building was located in front of the apse, in the center of the transept.

After the sides had been altered to correct irregularities in shape inherited from the 3rd century modifications, it was covered with marble decorations similar to those covering the apse. Its façade was divided into two parts. A golden cross bearing the names of Constantine and his mother Helena was placed in the upper part, and the lower section was closed with a double door. This door opened into a small area where, at least by the end of the 4th century, an opening in the floor was made, enabling visitors to lower objects on to the earth inside the small cavity below. This design, which still exists in the present Niche of the Palliums and is typical of the veneration practiced at the tombs of martyrs, is an extremely significant element of the tradition intimately linking the small monument to the site, immediately below, of Peter's tomb.

Gregory of Tours gives us a picture of a pilgrim lowering into the small shaft a cloth which would touch the Apostle's tomb and thus become a relic of it. The mediaeval liturgy placed a censer there for the whole year from 29 June to 29 June. The temporary placing of the Palliums in the niche, a custom still observed, is a further indication of the respect in which this spot was held.

Around the monument of Peter, four spiraling columns of sculpted marble connected with the balustrades, likewise of marble, formed the supports for a baldacchino crowned by architraves and arches. Two other spiraling columns at the angle of the apse were connected to the other four by two architraves. But the six columns of the baldacchino were not alone in stressing the importance of the monument of Peter in the Basilica. The plan of the Basilica itself also marks its importance. The architectural works just described are not only in front of the apse but also at the center of the transept.

This architectural fact is in itself unusual. Churches with transepts "in the form of a cross" may be familiar to us, but the historian notes that, among all the marytria-basilicas of the Near East and of Rome in Constantine's time, the Vatican is the only Basilica which has this design, a design later to be spread by the Carolingian renaissance. In the Vatican Basilica the transept was, in fact, the martyrium, the structure centered above the martyr's tomb and reserved for liturgical functions, as opposed to the five aisles reserved for the assembly of the faithful. The martyrium was a huge rectangle, 87 metres by 18, separated from the aisles at the time by a large central triumphal arch decorated with a mosaic showing Constantine offering the building to the Saviour, and by four arch-shaped openings on the sides. Taken together, the naves were 91 metres long and 64 metres wide. Besides the six columns of the baldacchino, 100 simpler columns taken from a variety of ancient monuments (as was much other material for the Basilica), in groups of 22, separated the aisles, or were placed at the lateral arch-shaped openings to the transept and at both ends o the transept. The entrance of the Basilica, a portico 12 metres wide, was preceded by a quadriportico 62 metres by 46, reached by 35 steps.

We have roughly sketched out what was by the will of Constantine the new architectural setting for the tomb of Peter. The Basilica, demolished by the Renaissance on the pretext that it was in danger of collapse, and precisely on the spot where it rested on the highest substructures, had certainly been damaged, but just as certainly it had been improved. Canons of the Vatican, architects and artists have fortunately left numerous testimonies which opportunely complete the information furnished by the recent excavations. We hesitate to stop here: certain stages of these changes, the first ones and the last, are essential to our subject matter.

The solution which Constantine's architects decided upon was the best - if not the simplest - which could have been chosen for a cemetery-basilica ad corpus, which was both a grandiose burial monument built around a tomb and a cemetery set aside to receive the bodies of the dead who wished to be placed near a saint's tomb, as was done in the catacombs. This burial characteristic is certainly a primary one for the Vatican Basilica. The solution of Constantine's architects nevertheless presented a serious inconvenience, since even then the influx of pilgrims made evident the need for regular liturgical functions. The monument and its baldacchino took up too much space in the middle of the transept. To his credit, Gregory the Great solved this problem with an architectural device which respected the monument as ingeniously as had that of Constantine's architects.

The problem was to establish a permanent altar at the center of the transept, easily accessible and perfectly visible, without touching the monument. The area immediately surrounding the Petrine monument, apse included, was raised about one and a half metres, while the top of the monument was transformed into an altar, without doubt the first permanent altar of the Petrine tomb. Four small columns placed on the altar allowed for the construction of a baldacchino. Nevertheless, the monument of Peter remained accessible, as before. Not only was it still completely visible from the central nave, separated from it only by the six columns of the ancient baldacchino now place in a single row and crowned by an architrave, but also two stairways permitted direct descent from the new presbyterium. In addition, under the presbyterium an original architectural contrivance had been built. Extending along the interior of the apse wall, an almost circular corridor, reached from the transept by two doors, led to a chapel, likewise underground, built directly behind the small monument and for that reason called ad corpus in some mediaeval texts. About two metres high (thus it was a little lower than the height of Constantine's construction), the new design, properly called the "Confession", gave a completely new appearance to the Memoria Petri. The ancient Basilica underwent only secondary changes. Under Gregory III, a second row of six spiraling columns of sculpted marble in the same style as the others was placed parallel to them. Under Calixtus II a new altar was constructed above that of Gregory the Great.

We noted above that the design of the Basilica with transept created at the Vatican by Constantine's architects spread throughout religious architecture from the Carolingian renaissance onwards. The architectural contrivance of Gregory, consisting of an altar-tomb and a presbyterium-crypt, imposed on the Vatican by liturgical needs and the requirements of a burial monument which was not intended to be touched, became almost instantaneously the model for builders of churches where the body of a saint was venerated, even if they did not have the problem of a pre-existing tomb in the edifice under construction. We may add that, from its time of construction onwards, the "uncovered Confession" which was to be built under Clement VIII and Paul V would become a prototype for similar constructions, imposed, and most often wrongly, on some altars in Roman Basilicas, including in the 19th century the altar of the Basilica of St. Paul-Outside-the-Walls. But it seems to be beyond our purpose to stress the different manifestations of the attraction which Peter's place of pilgrimage has had on religious architecture.

What we have hitherto described of the history of Peter's tomb at the Vatican shows that this history was dominated architecturally by a desire to keep the tomb intact. It is very tempting to state that this concern was equally dominant in the most delicate phase of this history - the construction of the present Basilica. The first measure taken at that time was dramatically of a preservative nature. In 1507, temporary walls joined to the apse wall permitted the setting up of a small construction which protected the papal altar until 1592. It was only under the pontificate of Clement VIII that the first part of the present architectural contrivance was constructed. The floor of the new Basilica, raised 3.20 metres above the previous floor level, required a corresponding raising o the 13th century papal altar. A new altar, the present one, was superimposed over the altar of Callixtus II. At the same time, the "uncovered Confession" with stairways maintaining direct access to the Niche of the Palliums was also constructed. Paul V added little to its present appearance. But Clement VIII did not limit himself to external modifications of the Petrine Memoria. Preserving the underground contrivance of Gregory the Great, he adapted it. On the outside of the almost circular corridor of Gregory, parallel to it and bordering the outside of the wall of Constantine's apse, a new circular corridor was built. Access was still assured from the crypts previously added according to the plans of Michelangelo between the floors of the two Basilicas. This new corridor, an essential element of what is called the new crypts, preserved access to the chapel ad corpus of Gregory which, since his time, had been enlarged a little and given the name "Clementine Chapel". It is in this small chapel, at the end of which still stands the small 7th century altar ad caput, as it is called, and in the two adjacent areas that the small burial building of the middle o the 2nd century presents for our reflection and devotion the first architectural testimonies preserved for us by a history which, until the recent excavations, had been concealed, as well a preserved, by the Niche of the Palliums.

Following the changes made by Clement VIII, a final architectural note needs to be made so that we can place in the new and prestigious setting of the present Basilica the ancient Memoria, which is somewhat lost in the immense space of the new edifice even while remaining its center.

Urban VIII's authority and Bernini's art carried out this final stage, through the construction of the bronze baldacchino of the altar which bids the onlooker to unite inseparable in his vision Michelangelo's dome with Peter's tomb. Eight spiraling columns which surrounded that same tomb in the ancient Basilica are included in the four pillars which support the dome and these columns, surrounding the baldacchino of bronze which was inspired by them, remain a witness to the continuity which we are striving to bring out.

It has been described above how the history of the Vatican Memoria of Peter is dominated by the constant desire to keep it intact. No less abiding is the wish to keep it visible and to ensure direct access to it. These aims seemed particularly evident in the Constantinian Basilica, both at the time of Construction and during the changes of Gregory, but these desires were already asserted, as we have seen, in the middle of the 2nd century when the small burial monument with niches and columns was built. Let us now add that these same imperatives were, at the price of a whole series of projects and plans, the final determining elements for the construction of the present Basilica.

An architectural tradition thus permits us to go back as far as the middle of the 2nd century; it is centered on a burial monument considered without interruption to be the one built above Peter's tomb. Yet our aim would remain unachieved if we did not present, in the light of the excavations made under and near the Basilica, the essential points of the record which could be described as the archaeological setting of the site of Peter's tomb in the first two centuries.

To begin with, it should be observed that, in giving a strict explanation, it would be better to talk here about the location of the tomb rather than about the tomb itself. In fact, the excavations did not discover the remains of Peter's body as it was buried after his martyrdom. Moreover, no archaeological element retrieved from the small cavity next to and below the Niche of the Palliums can be considered as belonging to a burial monument, however modest, of the 1st century. Yet it would be wrong to conclude that the recent archaeological investigations have added nothing to the history of the first decades of the tomb.

First of all, the investigations established that the 2nd century necropolis had been built beside a secondary road running directly along the northern border of the Circus of Caligula and Nero. It is equally clear that the family monuments which were part of it were built in an area already in use as a burial place. In the immediate surroundings of the Petrine monument there have been found piles of bones taken from previous tombs. These remains had been gathered together by the 2nd century masons, who did not take great pains to respect the material arrangements of the tombs in question. They seemed to be acting according to the customs prescribed by law. But this fact, hitherto hardly noticed, throws some light on what may have happened to the Petrine tomb at the moment of the construction of the small monument with niches. Under that monument only the remains of the body of the Apostle-martyr would have been collected. Did they remain there until the time of the construction of Constantine's Basilica? Had they already been moved in the middle of the 3rd century, when the monument underwent important changes? Our present purpose does not include answers to these questions.

On the other hand, it is important to stress that although this Vatican area was imperial property in the 1st century, it was then lined with roads beside which other burial grounds have been discovered. In particular, a small part of the most important one was unearthed in Vatican City at the time of the construction of a garage. It remained in use during the first four centuries and was located beside the ancient Triumphal Way. It included, in particular, two tombs which according to their inscriptions date from the reign of Nero. Further excavations have led to the discovery of some burial monuments of the Flavian age on the south side of the Circus.

But in Rome it is without doubt along the Ostian Way that the true archaeological and architectural parallel to the history we have been tracing is found: the tomb of the Apostle Paul and his two Basilicas. Concerning the second Basilica, built at the end of the 4th century and destroyed by fire at the beginning of the 19th, the reconstruction which respected the essence of its design gives us a precise enough picture. Concerning the first, built by Constantine, the excavations carried out at the time of the reconstruction tell us that it was of modest proportions. There, too, Gregory the Great raised the presbyterium and designed a crypt, limited this time to a chapel ad corpus located behind the altar and reached through a door. And, as at the Vatican, the tomb is situated in the middle of a pagan necropolis, but this time it is inside a family monument. We are obliged to end these pages dedicated to Peter's tomb by a visit to Paul's, since the true Roman pilgrimage ad limina has never consisted of anything other than a visit to the two tombs of the Apostles, "at the Vatican" and "along the Ostian Way". This was expressed at the end of the 2nd century by the priest Gaius, and at the beginning of the 5th century by the Spanish poet Prudentius - Gaius to justify a point of Roman ecclesiastical discipline and Prudentius to present the two Apostles as the guarantors of the faith of Rome. Thus the history of the two tombs has been, through nineteen centuries, a matter of parallel faithfulness to those who, by their common presence, their common preaching and their common martyrdom, "laid the foundations" of the Roman Church in the faith of Christ.

On the vault of the Constantinian apse, did not the mosaic erected by Pope Liberius exalt the divinity of Christ, as the bordering inscription indicates, and are not Peter and Paul standing together on either side of Christ in order to be the first ones in Rome to proclaim his divinity?

Jose Ruysschaert

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