The restructuring and re-flooring of the chapel incorporated into the farmhouse of the same name brought to light the remains of an earlier cult building, identifiable as the church of S. Ambrogio known in documentary sources of the 12th century. Excavations identified the cobblestone foundations of a small horseshoe-shaped apse that was not very deep and had a diameter of about 2 m. The arrangement of the cobbles in a herringbone pattern in the upper part of the walls suggests the existence of a second building phase to which the rebuilding of the presbytery area, including the construction of two side apses, probably dates. Only the southern side apse was documented. This type of church with three apses and a single nave can now be certainly dated to the 9th-10th century, also based on many parallels in Piemonte. Visible to the south was the western continuation of the perimeter wall covered by the foundation of the later chapel that had heavily reduced the width of the earlier building. The presence of a nearby Roman settlement, already indicated by past finds and the toponym _Amphorianum_, seemed to be further confirmed by a very worn marble slab (115 x 75 cm and 9 cm thick), framed by two incised lines, reused as a threshold, and by several fragments of large Roman tiles, found in the foundation trench of the chapel’s facade. This hypothesis is also supported by the find, in the past, in the vineyard in front of the chapel, of a marble fragment showing a flower with four bi-lobed petals and central button highlighted by three grooves within a round frame. This may have been part of a decoration with _anthemia_ of a lateral pulvin from the top of a funerary altar. The opening of a trench parallel to the chapel’s facade, to the exterior, did not reveal any remains of the ancient church but only of two pits from different periods. The latest of the two was filled with residual imbrices from the modern re-roofing; the earlier pit was filled with Roman painted plaster, imbrices, and tegulae, and on the bottom, a broken marble slab. The few medieval finds, mainly relating to soapstone and plain buff ware pottery in use between the 11th and 13th centuries, confirm the absolute dating of the sequence for the construction phases of the chapel built in the 13th century between the outbuildings of the abbey of San Dalmazzo di Pedona.