The Heiligenberg has sometimes been identified with the Mons Piri mentioned by Ammianus Marcellinus, where in 369 forces of the Roman Emperor Valentinian I dug trenches but were repulsed by Germanic tribesmen. There are isolated finds from the 4th and 5th centuries, and the mountain was then resettled in the late 6th century. Demonstrably Christian burials appear there by the late 7th century, and in the 8th century, during the Carolingian period, stone buildings were erected over the Roman shrine. They may have been for the use of the king's representatives.