Emperors Constantine and Valentinian safeguarded the frontier by constructing fortresses in Koblenz are (Confluentes) and Boppard (Bodobrica) with strong walls and round towers, of which remnants remain.

In the 5th century, the Alamanni and Franks forced the Romans to withdraw from the area. They took over the Roman cities and the Franconians began founding new cities of their own. Unlike the