According to reports by Giovanni Battista Biancolini beginning in 750 the complex served as an episcopal see for the diocese of Verona until 804, when church and monastery were destroyed "ab infidelibus hominibus," perhaps Huns or Avars but more likely Frankish insubordinates or Arian survivors.

[6][note 1] Not much is known about the books kept there but it is certain that the monks received from Pepin as gifts, in addition to land and objects of worship, "Gospels written in pen all adorned with gold and with precious gems.

"[7] In addition, in 1940, two manuscripts were found that were certainly part of the monastery's library, Justinian's Institutiones and St. Augustine's Tractatus in Ioannis evangelium, with the latter being annotated "Liber monasterii Sancti Zenonis Maioris de Verona.

In spite of this, the monastery continued to grow throughout the 12th century and was promptly rebuilt in the forms and dimensions that still distinguish it today, according to the taste of the Veronese Romanesque style in vogue at the time.

The prosperity enjoyed by the monastery was a consequence both of the gifts it received from the faithful and the diocese, but also and above all of the numerous privileges granted to it by the various emperors over the centuries, first by the Carolingians, then by the Ottonians, and then by the Hohenstaufen; the last one of which is known was issued by Frederick II of Swabia in 1221.

[9] In 1226 Ezzelino III da Romano seized power in Verona and throughout the March of Treviso, subjugating even the religious community of San Zeno, creating rifts within them that manifested themselves in a substantial loss of autonomy in favor of the lay members of the municipality.

With the coming to power of the Scaligeri, the autonomy of the convent was further reduced, so much so that, in 1292, Alberto I della Scala was able to impose his illegitimate son Giuseppe as abbot, instead of a "real" abbot; in this regard Dante Alighieri mentions Giuseppe in Canto XVIII of Purgatory condemning him to Hell, a judgment that historians consider far too harsh, considering that Giovanni worked to increase the number of monks present, revised the documentation and began work on the new abbey palace and the present cloister.

[note 2] A second inventory of codices contained in the monastery, listing 131 of them, is instead dated May 12, 1400,[15] and was compiled by the Brescian Giovanni De Lantanis, a student of liberal arts at Sorbonne in Paris, at the behest of Pietro Emilei, abbot of San Zeno between 1399 and 1421.

[16] These inventories allow one to assume that throughout the 14th century the scriptorium was in full activity and was also directed to provide a service for private individuals in addition to that related to worship; it has even been proposed that many of the amanuenses were laymen or at least not monks.

[18] Following this there was a loss of power on the part of the local aristocracy in favor of the officials of the Serenissima, a fact that also affected, albeit indirectly, the San Zeno complex.

[20] Among the deeds arranged by Emilei it is stated with regard to the library, "cum loco ibidem pro Libraria," that it was located in a room situated between the granary and the bakery demonstrating that the number of codices was so great that they could no longer be kept in the sacristy.

It was also to grow considerably between 1445 and 1464 when the commendatory abbot was Gregorio Correr, a great supporter of culture and the commissioner of Mantegna's San Zeno Altarpiece, which is still preserved inside the church.

[24] It was, however, the commendatory abbot Pietro Contarini who opposed this idea by introducing four Vallombrosian monks into San Zeno from the nearby church of the Holy Trinity and going so far as to accuse Don Mauro of stealing documents, thus having him imprisoned.

On the entrance door of the monastery library the monks placed an epigraph to commemorate Priuli's generosity to them, on which is written "PRAECLARUM HUIUS BIBLIOTHECAE CUM DOTE // UNCREMENTUM ALOYSII CARD.

[30] According to reports in the treatise Beschreibung Verschiedener Biblioteken in Europe by the priest and librarian Adalbert Blumenschein (c. 1720–1781), it seems that this library was still in the convent and was only rarely accessible to scholars, perhaps only twice every three months.

With the subsequent acquisition of the church of San Sebastiano, this intention could be acted upon, and so in 1792 the Civic Library of Verona was born on the basis of the book collection from the monastery.

A privilege of Emperor Henry II the Holy in 1014 allows one to know the exact extent of the territories over which the abbey had jurisdiction at that time: the villages of Ostiglia and Villimpenta with adjacent woods, the castles of Moratica (today in the municipality of Sorgà), Erbé, Trevenzuolo, Vigasio and Romagnano,[33] plus several scattered properties, even substantial ones, such as in Bardolino.

"[33] Around the basilica, moreover, came to form over time the settlement of the same name over which Emperor Henry IV, in 1084, gave full jurisdiction to the monastery; the territory was much larger than just the village but extended from the (destroyed) church of San Martino Acquario, on which Castelvecchio would later be built, to Chievo.

However, some sources mention as part of the territories of the monastery of San Zeno a locality called Vallis Trusa or Strusa, which is most likely a mountainous area of Baldo overlooking Caprino Veronese.

Finally, in a 1221 diploma by Frederick II, he confirms San Zeno's possession of Valle Trusa and Costa Blota, that is, the part of Mount Baldo immediately above Caprino.

In Henry II's diploma of 1014 the church of S. Vito in Curia Venti, i.e., in the present locality of Porto di Brenzone, appears as a possession of San Zeno.

[56] Thirteenth-century documents reporting canon payments to San Zeno show that among the lands leased (and thus belonging to the monastery) appear the localities of Malcesine and Brenzone[citation needed] and Castion (Costermano).

The present church, built on the site where at least five other religious buildings had previously stood, maintains its medieval origin substantially unaltered, representing an example of Veronese Romanesque architecture.

[66][67] Below the chancel, at the lowest level of the entire building, there is a large crypt whose ceiling consists of 54 rib vaults supported by arches resting on 49 columns.

[68] Also noteworthy are the bronze panels on the portal, the work of several medieval master foundrymen, and the large rose window on the facade, called the "Wheel of Fortune", made by the stone mason Brioloto de Balneo.

This complex, which had the access to the monastery on the ground floor, was intended for the abbot and the most prestigious guests, as the abbey until even the 14th century served as a hotel for the emperors of the Holy Roman Empire.

On the perimeter walls of the ambulatories are placed sarcophagi and tombstones, among which the tomb of Giuseppe della Scala stands out, dating from 1313 and enriched by a lunette with a fresco by a painter of the Giotto school.

[76] On the same wall opens a door that allows access, by descending a few steps, to the so-called sacellum of St. Benedict, above which there is a lunette frescoed in the late 14th century with a Madonna with two bishop saints.

The name "St. Benedict" comes from the fact that in 1723 a plaque was found whose engraving told how a monk of the abbey had had "hoc opus ecclesie sancti benedicit" built at his own expense.