[3] The early church – built in the style typical of the earliest Christian worship halls in the Po Valley region between the mid- and late 4th century – was a single hall measuring 24 x 16.5 meters, identifiable through a layer of red marble in the floor of the present church,[4] and was decorated with a rich mosaic pavement consisting largely of votive offerings, partly preserved and brought to light, along with part of the foundations, in the mid-20th century.

This building shows how the Christian community of Vicenza had already achieved considerable importance in the first half of the 4th century, as evidenced by the fact that a senatorial family also contributed to the construction of the mosaic floor.

The sacellum – one of the most remarkable and best-preserved early Christian buildings in Italy – was built shortly after the mid-5th century and was originally meant to correspond to the Martyrion intended to house the basilica's relics.

Matris Domini Gregorius sublimis vir referendariusa fundamentis aedificavit et in Christi nomine dicavitIt continued to function as a place of worship for the martyrs until 1674, the year in which, when the complex was renovated, it was transformed into a service room for the adjoining monastery; windows were opened and the original small windows closed, the portal remodeled, the marble covering removed, and, most importantly, the martyrs' remains were moved to the crypt of the basilica and placed in opulent Baroque-style gilded wooden reliquaries.

[18] In the year 899, during one of their raids, the Hungarians destroyed part of the city and set fire to the abbey; the monks scattered to several places, abandoning discipline and neglecting the divine office.

[20] A few years later, with one of the most important acts whose documentation has been preserved, the Privilegium of 983, Bishop Rudolf, a staunch supporter of the Cluniac Reforms, donated to the Benedictines of the Abbey – or rather partially returned, since these were goods already in their possession that had passed to the Bishop at the time of their expulsion by the Hungarians[21] – a considerable amount of landed property, cum famulis et decimis, ranging from Ponte Alto to the mons famulorum i.e. Maddalene, from Brendola to Marostica.

Together with the lands, he entrusted to the Benedictines the administration of the territory, the pastoral functions and the reclamation of large swampy areas; it was the period of the encastellation and the monastery of San Felice also provided itself with a defensive tower.

The Benedictines of San Felice then founded numerous churches and small monasteries, also dependent on the mother abbey, generally placed along the ancient Roman roads leading out of the city.

[22] The Abbey of San Felice continued to receive numerous donations; of particular note is that of Bishop Jerome in 1013, who confirmed the privilegium of his predecessor Rudolf thirty years earlier; from this act it appears that the church and the monastery, recently rebuilt, were again half destroyed and abandoned, probably due to episodes of violence whose origin is unknown; like Rudolf, Jerome also wanted to restore religious life to San Felice, as a stronghold of the faith in the territory.

From this period on, they began to cede them to emancipated serfs or small feudal lords; at first this cession increased the early patrimony, but already in the 13th century the fragmentation of the lands led the abbey to an administrative crisis.

The Benedictines – as happened to the bishops in the same period – fell into the hands of usurers and were forced to sell many important properties, including those of San Vito and Malo.

[26] But even after the fortunes turned in favor of the Pope, donations and privileges continued to be granted to the abbey, which remained the heart of Vicenza's religious life until the middle of the 13th century.

[31] Under the Scaligeri – who had confiscated all the property of the local Church, including the rich patrimony of the monastery – the monks and servants lacked even food and clothing, so much so that Abbot Bernard complained that he could not maintain a good standard of religious life or even ensure the divine office.

[32] The basilica, rebuilt in 983, remained basilical in plan – with three naves separated by two rows of pillars leading from the entrance wall to the shoulder of the apse – and there are no traces of a crypt, as was common in the churches of the time.

[33] Both the bell tower and the church were severely damaged by the violent earthquake of January 3, 1117, which struck all of northern Italy: reconstruction began immediately under the direction of Abbot Albert, who is commemorated in a marble fragment kept in the Parish Museum.

Towards the end of the 12th century, Bishop Cacciafronte, who was particularly devoted to the patron saints of the city, had the ancient Roman road – a section of the Via Postumia – that led from the Cathedral to the Basilica repaired at his own expense, since the cobblestones had worn away over time and made the passage very uncomfortable.

[36] The new religious policy of the Republic of Venice led to the restoration of the ecclesiastical patrimony, which had been disturbed and largely dispersed during the rule of the Scaliger and Visconti families in the 14th century.

In order to maintain it in a decent state during those times of general upheaval in the Church, it was given in commendam to foreign abbots, who were assisted in this task by only two or three monks; around 1430 these were mostly Germans.

In less than ten years, the number of monks increased to sixteen, coming from different parts of Europe, despite being located in an insalubrious place near the stagnant waters of the river Retrone.

[39] The reform wave of the Council of Trent, which Bishop Matteo Priuli also tried to bring to the city, was not immediately accepted by the abbots of the ancient monasteries, especially that of San Felice, who opposed the decrees, considering them detrimental to the apostolic privileges and exemptions they had acquired.

In the second half of the sixteenth century, San Felice had a patrimony with the highest income among all the monasteries of Vicenza, despite the fact that over time it had had to sell many of its assets, lands[40] and even relics, even going so far as to propose to its creditors and moneylenders the celebration of Masses of suffrage, quantified until the debts were paid.

In the first half of the 18th century, however, the monastery, which by then had been battered by time, lack of maintenance and the earthquake of 1695, was completely restored and partially rebuilt during the period when Dom Floriano Serta of Vicenza was abbot.

The upper part of the façade is softened by a loggia in bas-relief, divided by pilasters with stone columns and pairs of small arches, the workmanship of which, similar to that of the bell tower, testifies to its construction in the 12th century.

It is a square with a composite clipeus in the center, surrounded by a double coil and the inscription Felix cum Toribius et Immola, probably the names of the people of senatorial rank who commissioned it.

According to the testimony of the Vicentine historian Francesco Barbarano, a templon, supported by four small columns resting on plutei,[64] separated the faithful from the sacred space where the relics of the martyrs were kept, and contained the dedicatory inscription to Maria mater Domini.

Of great value are the early Christian mosaics found in the corners of the central quadrangle: the remaining fragments reveal the presence of a particularly refined mosaic apparatus – which originally covered the dome, the splays, the archivolts and the semi-dome – rich in details executed with great precision: they represent a winged lion and a clypeate saint, that is, inserted in a clipeus, depicted according to the stylistic features of the Hellenistic period.