A preliminary excavation in the courtyard behind the church of S. Matteo, during the construction of a new oratory, provided new data to add to that, which emerged during excavations in the cellars, cloister and courtyard in front of the rectory between 1993-1994. This area corresponds with the ancient forum of Dertona adjacent to the structure known as the “mausoleum of Maiorano”.

The deep stratigraphy revealed five main periods documenting the area’s use from the 1st century B.C. onwards, with the creation of a monumental paved piazza directly on levels of sterile alluvial material, of which, thanks to this intervention, it was possible to identify the continuation towards the south.
Substantial robbing of the building materials and the quarrying of clay below it attested the forum’s abandonment. This was followed by the construction of a wall, the creation of a small necropolis of burials in stone-brick lined tombs in which no grave goods were present, and the building of a timber house associated with middens containing Lombard pottery with stamped decoration.

The foundation of S. Matteo, a church of the Canons Regular of the Holy Cross of Mortara, known from documents of 1134, saw the continuation of funerary use in the area and the cemetery was extended into the vegetable gardens in at least the 13th century. The adjacent remains of timber planks, of which traces of supports for the roofing were also preserved, seem to date to the same period. The subsequent transformation of the area, culminating in the construction of the Domenican monastery between the end of the 17th and beginning of the 18th centuries, was characterised by an accumulation of layers and building of structural elements relating to settlement use following the partial reclamation of the cemetery area attested by two large pits filled with human bones. In the modern period, heavy robbing of the 18th century structures and rubble dumps preceded the construction of an auxiliary building for the church complex that was demolished during the recent works.