The site of Castelletto Monastero, in the diocese of Vercelli, stands on the boundary between the modern provinces of Biella and Vercelli on the edge of a “baraggia” terrace (a geological formation of alluvial origin, covered by wasteland with spontaneous vegetation) where the Cervo and Ostola torrents meet. The area, occupied from at least the Roman period – as attested by evidence of burials and settlement – was crossed in antiquity by a network of tracks linking the upper Vercelli plain with the alpine areas of Biella and the Valsesia. These tracks were also used, at least in the medieval period, for transhumance. A Cluniac priory stood on the site, first mentioned in a document of 1092, although there is mention in 1083 of the Burgundian abbey at Castelletto, which owned estates in this area. The foundation of the monastery was also linked to a dynasty of functionaries, the counts of Pombia (later Biandrate) who, between the 11th-12th century, increased their presence in these territories and consolidated their power. Today the area still preserves standing remains of the monastic complex, visible in the church of SS. Pietro e Paolo (transformed into a parish church in 1593, after the priory’s suppression) and in a number of related structures, in particular: a forepart abutting the church façade, its earliest phases probably dating to the 12th century; the orthogonal structure to the church itself, part of the cloistered area; a building east of the church and parallel to it, probably the second church of the priory following the Cluniac model. During the summer of 2009 the Dipartimento di Studi Umanistici undertook a first excavation campaign in the courtyard area which opened along the south side of the church, over a surface area of circa 275 m2. When the surface deposit had been removed numerous walls appeared mostly on a parallel and orthogonal alignment to the church’s south wall. Around the end of the 18th-beginning of the 19th century all were razed to a uniform height (circa 15 cm below present ground level) when a cobbled paving was laid. Almost the entire area was covered by an earth dump, between 30 and 50 cm deep, which sealed the ancient stratigraphy. The upper levels of this stratigraphy were exposed at the end of the campaign, following the removal of the dump and will be investigated during the next excavation. The numerous pottery fragments found in secondary depositions within the dump dated mainly to the late medieval and early modern periods and probably relate to the phases exposed and not damaged by the late 18th century interventions. The emerging walls were almost exclusively built with cobbles, some placed in a herring-bone pattern, bonded with mortar. However, other construction techniques were seen in a square room built of cobbles bonded with clay, its corners reinforced with brick, and a brick wall bonded with earth forming the northern limit of a floor in hollow clay tiles. The latter was very well preserved and was only partially exposed as it extended to the south beyond the excavation edge. For the moment the walls, although they cannot be related to specific buildings, document a fairly well organised layout in the area probably occupied by the cloistered structures, with a diachronic development attested by the diverse phases visible in the walls themselves. This is of particular interest due to the lack of documentary evidence for the layout of the complex (sectors not destined for cult use) until the 19th century.

Excavations begun at the Cluniac priory of Castelletto Cervo in 2009 continued in the area investigated in that year (area 500: courtyard south of present parish church, previously a prioral church, datable to the end of the 11th century). Two new trenches were opened in the area north-east of the church. Trench A was placed in correspondence with the eastern end of the north nave – a rectilinear wall resulting from late medieval alterations which obliterated the end of the ancient presbytery. Trench B was placed up against the eastern end of a building standing to the south-east of the church itself, now used as a warehouse, but probably originated as the monastery’s second church. Continuation of the excavations in area 500 exposed the majority of the structures identified in 2009, and clarified, at least on the level of a working hypothesis, the organisation of the area and its development during the medieval and modern periods. In particular, the presence of two parallel main walls was documented, lying at a right-angle to the church and on a north-south alignment. They appeared to belong to the same construction phase and were perhaps part of the east wing of the Romanesque cloister. Immediately to the east, a number of burials were identified within a walled space that may have been a gallery forming part of the cloister. The burials were in tombs made with cobbles and brick, with a pitched covering and dated to at least two periods in the development of the funerary area, which was in a privileged position. Following the Romanesque period, to which the structures described above can be attributed, the excavation documented traces of building interventions involving the cloister-arm, which, among the other alterations, was divided into two rooms by a cobble and brick wall. The wall was associated with a floor and brick facings, structures already uncovered in the previous campaign. In correspondence with the building’s western entrance, two substantial parallel walls were built to the west. These were characterised by the same construction technique (cobbles with squared and levelled stones at the top) and were built to protect/monumentalise the entrance itself. The final phases, preceding the radical transformations occurring between the 18th and 19th century for the creation of the cobbled surface identified in 2009, were represented by the construction of two small rooms with cobblestone walls bonded with clay and by signs of substantial robbing. In the area behind the church Trench A revealed as shallow portion of the northern apse, datable to the first phase of the monastic complex (end of the 11th century), built of cobbles and mortar. At the same time a wall on a diagonal with respect to the other alignments within the layout of the Romanesque monastery was noted. This may have belonged to a pre-existing structure. The foundations of a deep apse, built of cobbles and mortar, came to light in the sector abutting the building to the south-east of the present parish church. This confirmed the hypothesis identifying the structure as the second prioral church. Almost on the same median line as the apse, to the east of the latter, there was a wall associated with a second perpendicular wall, of which a section was preserved, which could belong to an attached room, if not dating to a period preceding the construction of the church. A burial in an earth grave was identified in the area, but not excavated.

The 2011 excavation concentrated on the courtyard area to the south of the present parish church, formerly the priory church. The work took the excavations begun in previous years down to natural and also opened a new area, further towards the interior of the large open space, continuing on from the northern half of the cloister’s west wing, also investigated in previous years. The presence of a cloister to the south of the church was confirmed. The structure was arranged around a central open area, surrounded by colonnades (the west and north of which were identified abutting the southern perimeter of the church), which in turn bordered the buildings in which the daily life of the religious community took place. In particular, the excavation exposed the western wing of Romanesque date, at least 20 m long, and identified the point where the south-western wing joined it at a right-angle. At the point where the two buildings met, in the south-western corner of the cloister, a system of water pipes came to light, the metal fistulae still partially in situ. The pipes passed under the perimetral Romanesque walls, in phase with them, linking the internal area of the cloister with the exterior, towards the edge of the terrace of uncultivated scrubland on which the monastery stands. These structures confirm the hypothesis that the complex was well-planned from its conception. The importance the monastery came to assume in the first centuries of its existence, even as regards its architecture, matches the development of its patrimony, as attested by the written sources. Its importance is also attested by the support of the lay aristocracy, whose presence is suggested, within the cloister itself, by the discovery of an inhumation burial inside a brick coffin, in the west wing. The tomb contained a prick spur with related buckle. The burial (containing two overlying skeletons) confirmed that the cloister colonnades were used for privileged burials, as previously documented in the western colonnade and is now known for the northern gallery, where further burials in brick coffins datable to the same period have been found. Furthermore, the monastery was built on a site that seems to have been occupied in an earlier period, although at present it is difficult to define these phases of which numerous traces, including structural, were found during previous campaigns. More information about these early phases came when occupation levels were reached, containing numerous fragments of soap-stone, cut by the foundations of the Romanesque priory, and with the discovery of a small quadrangular room at the centre of the cloister area. The latter was associated with a cobble surface whose function remains to be clarified. Regarding the developments in the full and late medieval periods, this excavation confirmed the evidence found in 2010, for example the tile flooring whose continuation to the south was uncovered, and acquired new data for the west wing of the cloisters in particular. Here, substantial alterations were seen, especially in the new internal divisions connected with the construction of a wall on an east-west alignment, linked to a channel, which reused sculpted and dressed stone elements. The channel entered the western perimeter wall of the Romanesque complex, attesting the latter’s progressive development until it was robbed in the modern period, sealed by its razing and the laying of the late 18th-19th century cobbled surface, uncovered in 2009 and whose continuation to the south was exposed during this campaign.

The excavations north of the forepart extended the trench opened in 2009 that had intercepted two orthogonal walls and uncovered, on one side a structure at a right angle to the church, at the point where the building met the forepart, and on the other more tombs relating to the lay cemetery area. The intervention identified walls USM 119 and 120, north of the church, as parts of the 19th century cemetery. Running along the western side of the trench was a brick wall with the remains of an entrance that would have had a single wing door (17th-18th centuries) and a rectangular building on a north-west/south-east alignment, whose function remains to be identified. Datable to between the 15th and 16th century, it was built on layers of rubble and had been covered by late 18th century dumps used to raise the ground level in this area. The late 12th/13th-14th centuries saw the development of the latest medieval cemetery phases (phase 3), subsequent to the construction of wall USM 122 and the forepart preceding the church; the tombs identified in 2009 relate to this phase. These were burials in earth graves, dug on different alignments without an ordered layout. Along the side of wall USM 122 running east to west, there was a group of infant burials (ranging from individuals of a few years of age to foetuses). This development was preceded, in the 12th century, by the construction of wall USM 122, with a sloping eastern face, in which there was a cart entrance with double door, for which the postholes were found. To the west of the cart entrance, was a road with a compact surface of cobbles and brick/tile, which from wall USM 122 continued to the west but was cut by the modern intervention to reclaim the cemetery area. The construction of wall USM 122, in phase with the building of the forepart, intercepted the intermediate cemetery phase (phase 2), characterised by earth graves, oriented east-west, in a well ordered layout but with overlying burials in the grave cut itself. This cemetery phase corresponds with the church’s construction, between the end of the 11th and the 12th century. The burials respect the alignment of an ancient road, also made of compacted cobbles and brick/tile which, coming from the north-west led towards the church façade. The earliest cemetery phase (phase 1) showed a different organisation of the burials, which were generally aligned north-east/south-west, in parallel rows. The tombs, partially covered by the road described above, were deeper and not on the same axis as the church. This may have been a group of early medieval burials. Excavations south of the second church concentrated on a structure whose position suggests that it was the monastic infirmary. The north and south perimeter walls were preserved, visible for over 10 m. They bordered a space of about 5 m, and to date represent the earliest, perhaps Romanesque, evidence for this sector. The structure presented modern alterations (it was divided into two rooms and then in the 20th century took on a rustic aspect) and late medieval restructuring when the floors were lowered and a paving was created using circular sections from a brick/tile column. During the same campaign, cleaning in the garden next to the east cloister revealed two connecting structures at a right angle to each other, similar to the cobblestone walls of Romanesque date previously identified as the intersection between the east and south cloisters.