Little or nothing is known about the early building, however some elements, such as its location in the area where the castrum of Theodoric the Great stood (in the vallum of the castle, hence the name), suggest that in the beginning it may have been the Arian cathedral of Verona, as opposed to the Catholic church of Santo Stefano.

During the following centuries the building did not undergo any other major transformations, however, it was deeply damaged during a World War II bombing raid; at the end of the conflict, therefore, it underwent extensive restoration.

The church building, which is one of the masterpieces of Veronese Romanesque style,[1] is characterized by a basilica plan divided into three naves by the alternation of pillars and columns, while the vertical development is on three levels: a raised presbytery, the hall and the lower crypt.

In the crypt, next to the high altar, are kept two valuable sarcophagi: one dating from the 4th century features a bas-relief sculpture on three sides in two overlapping orders with stories from the Old and New Testament narrated and in which tradition holds the relics of the apostles Simon the Canaanite and Judas Thaddeus; the other, which is older (2nd or 3rd century), is a strigilated sarcophagus from the pagan period with depictions in the center of two spouses in a shell above a rural scene and with two figures of philosophers later transformed into Christian saints on either side.

[5] Due to the fact that it stands not far from the castrum erected by Theodoric the Great and also later used by the Lombards, many believe that this may have been an Arian cathedral, as opposed to the aforementioned church of Santo Stefano, which may have been the Catholic one.

[8] Further confirmation of this comes from a document by Bishop Rotaldo dating from 813, at the time of the reign of Pepin of Italy, in which it is attested that San Giovanni was a Christian parish church equipped with a baptismal font.

[9] Bishop Rotaldo again received a privilege from Emperor Louis the Pious on June 13, 820, in which the church of San Giovanni in Valle was described as a simple oratorium, showing that it had lost its importance.

In fact, in 1756, thanks to Pope Benedict XIV's constitution Regis pacifici vices, San Giovanni in Valle was freed from the authority of the canons of the cathedral to be subject directly to that of the bishop.

[25] The church of San Giovanni in Valle stands in the eastern part of the city of Verona, on the opposite bank of the Adige River from that on which the ancient center is located.

The lunette underneath the prothyrum preserves remains of a fresco, depicting a Madonna seated on a throne with a baby Jesus on her knees attributed to Stefano da Verona.

The composition is completed by three medallions divided by a frieze, painted on the intrados of the prothyrum, inside of which are the figures of St. John the Baptist, the Paschal Lamb, and the Prophet Isaiah, all most likely made by the same author of the lunette.

In this regard Wart Arslan notes that "in the 14th century, with a respect for the ancient of which we do not have many examples, the church was lengthened, adding an additional bay while preserving the profile of the older facade, carefully restoring the crowning with arches to the new construction.

[34] The other two apses, made entirely of tuff, have no lesenes but feature a cornice with small arches, double lintels, surmounted by a sawtooth ornament and a finely carved frieze.

The frieze of the central apse, in particular, features a number of hunting scenes including some dogs chasing prey and a hunter playing a horn, all sandwiched between an interlacing of flowers and striped leaves, sometimes open so that a pistil or pine cone can be glimpsed: a motif that can be found in other Veronese architecture of the same period.

Master bell ringer Luigi Gardoni wrote in the act of testing (contained in his Memoirs) that "everyone in Verona will be discussing the beautiful concert that happens in San Giovanni in Valle."

[40][30] Today the area of the former cloister constitutes a small courtyard accessible from the public street through a wide iron gate near which was placed, around the 14th century, an aedicula housing a statuette, strange in its deformity, depicting St. John the Baptist.

[30][41] The interior of the church, with a three-nave basilica plan without a transept, is covered with timber roof trusses and is lower than street level by five steps (about one meter).

The interior space is developed on three levels: from the nave, access is gained to the presbytery located above via a wide staircase placed along the central axis about halfway up the church, while two smaller staircases, placed in continuation of the minor naves and covered by a barrel vault, provide access to the lower crypt; such a scheme can be found in other Romanesque churches in the province of Verona, such as Santo Stefano, San Severo, San Zeno, and in the Abbey of Villanova.

The two side aisles are separated from the central one by two parallel rows of round arches supported by a regular alternation, beginning with the second pair, of columns and pillars with a square base.

To the east, the crypt concludes with three apses, made of simple unadorned masonry, placed in continuation of the three naves; the left and central basins turn out to be decorated with frescoes of which only a few traces remain, worn away by time and moisture; in particular, one can distinguish depictions of the Madonna and Saints and of the Annunciation and Visit of the Magi.

At the four corners of the sarcophagus small statues stand in which some critics have identified the possible depiction of the apostles Simon and Judas in monastic dress and two women representing two virtues.

[51] Regarding this event, Count Ludovico Moscardo (1611-1681), historian and naturalist, in his Historia Di Verona (1668) remarked, "In this same time in the Church of San Giovanni in Valle were found the Holy Bodies of S.S. Simon and Thaddeus the Apostles, enclosed in a marble ark, which from some letters carved on them were known to be of those glorious Saints, which were devoutly visited by all the people of Verona, and shortly afterwards by public order there were carved in the same ark some figures and the names of the Saints.

In the center the strigilation is interrupted to give way to a shell in which are inserted the busts of two spouses looking at each other: the portrait of the husband, wearing a tunic, appears with marked realism, while in that of the wife the hair combed into braids according to the custom of the time stands out.