The complex of the Holy Trinity of Venosa is among the most important monumental sites in southern Italy. To make it unique the stratification of Roman, Lombard and Norman presences that emerge from the structures and tell centuries of history.

The large abbey complex consists of the ancient (or old) Church and the Unfinished (or new), whose construction was never completed. The hypothesis of its foundation still seems controversial. For some scholars it was raised by the Benedictines before the coming of the Normans. The original nucleus consists of an early Christian Basilica built between the fifth and sixth centuries, where previously there was a pagan temple dedicated to Imene. The Romanesque basilica in 1059 was consecrated by Pope Nicholas II; In the same year Roberto il Guiscardo wanted to make the church the shrine of the Altavilla and then had the bodies of his brothers Guglielmo "Popeye", Umfredo and Drogone (later he will also be buried here).

The ancient church has an early Christian structure with a basilical plant and a large nave with the apse placed on the bottom; this linear structure over time has undergone various changes from the seventh century, until the rebuilding by Longobardi (in the 10th century) and Normans (between the 11th and 13th centuries). The entrance of the church, in Romanesque style, is characterized on the left side by two sculptures of stone lions and four ledges, which correspond to as many facades superimposed on each other over the centuries. From right to left: the first ledge is from the Norman period between the eleventh and twelfth centuries; the second is Lombard, dated the tenth century; the third is from the eighth-ninth century and the fourth is the side entrance of the Early Christian Basilica.



The new or "unfinished" church was started with the use of materials from monuments of various civilizations present on site, including Roman, Lombard and Jewish. His project dates back to the twelfth century, when the Ancient Church was deemed an unsuitable place to contain a number of faithful, then it was decided to design a vast extension behind the apse, with the aim of creating a single large basilica. The works, financed by the Benedictines, began towards the middle of 1100 but the pace gradually decreased, due to the fluctuating heritage of the monastery and also because these were forced to leave Venosa, causes the suppression of their Monastery at the behest of Pope Boniface VIII in 1297. In the same year, he assigned the complex to the Knights of the Order of the Hospital of Saint John of Jerusalem (later known as the Knights of Malta), because they had lost their possessions in Palestine during the last Crusade. The Order paid no attention to the monastic structure of the new church and established its headquarters in Venosa, precisely in the "Palace of the Bailiff". Since then, the structure has not been completed