What is "zons"

Zons , formerly known as Feste Zons ( Fortress Zons), today officially called Stadt Zons (Zons Town ) is an old town in Germany on the west bank of the Lower Rhine between Cologne and Düsseldorf. It has been a part ( Stadtteil) of the town of Dormagen since 1975. In 2010 its population was 5,370.