The structure consists of four complexes: the ancient church, which stands on the remains of a Roman domus; the Abbey Palace, located on the right of the façade of the ancient church, consisting of the Foresteria and the Monastery; the Paleo-Christian Baptistery, dating back to the 5th century. d. C., and the most fascinating of all: "The Incomplete".
The New Church was built to replace the Ancient Church, considered inappropriate to welcome the faithful, given its small size. The works, begun in the mid-1100s and financed by the Benedictines, were never completed because the monks were forced to abandon Venosa because of the suppression of their Monastery by the will of Pope Bonifacio. The Pope then assigned the complex to the Knights of Malta, but placing them inside Venosa in the Palace of Bali, the New Church did not complete and was entrusted with the name he still carries.
The structure is made up of a longitudinal body, with three aisles, with a wide protruding and acessed transept and a very deep chorus surrounded by a deambulatory with radial chapels. The entrance, passing a semicircular arch, highlights a lunette decorated by a propitiatory inscription that calls for God's protection of the church and monks. Above the lunette lies the lamb with the cross, which is the symbol of the Order of the Knights of Malta.
Within the Incomplete I can find various works and ornaments that belonged to the Roman Amphitheater, such as the epigraph of the gladiatorial school of Salvio Capitone, which presents a list of gladiators who fought in the Amphitheater. During the sixteenth century the large sailing bell tower was built on the right side. On the side facing the inside of the Incomplete, just below the bell level, there is a stone walkway, supported by a series of hanging arches on small shelves embedded in the masonry.