 Documents verify a "Fronhof" of the archbishop of Cologne (Fronhof = estate of a feudal lord receiving socage) existing in Zons at least since the beginning of the twelfth century .In the 1980s archaeological excavations in the castle area uncovered foundations of buildings which are regarded as remains of the proprietary church of the lord of the manor which was part of the building complex of the "Fronhof".At about the middle of the thirteenth century Zons "castrum" (castle) was fortified.