The site is situated on the southeastern edge of the plateau of “Mageroux”, dominating the confluence of the Vire and the Ton, where the Gallo-Roman vicus of “Vertunum” used to be. The existence of a first stone church, which might have dated from the 8th century, has been discovered through excavations. It was destroyed and replaced in the 9th or 10th century by a barely larger church which was solidly built with re-used blocks. In accordance with tradition, the church was oriented to the east, i.e. in the direction of the “Orient”. Important remains have been conserved: the northwestern and southwestern freestone quoins, the northern wall bearing a gutter, which includes two sculpted blocks of the Early Roman Empire. In the 10th or 11th century, this second church was extended to form today’s nave. One can still see the link between both parts. In the 11th and 12th century, the rectangular nave, which had been heightened by a metre, was extended once more with a square chancel to form the Romanesque church. In the 13th century, a keep tower was erected against the western wall of the nave. Two private chapels and a sacristy added in the 17th century completed the building.