History of the Jews in Cologne

The history of the Jews in Cologne dates to 321 C.E., when they were first recorded in a census decreed by Emperor Constantine I. As such, it is the oldest European Jewish community north of the Alps. The community quickly established itself in what came to be known as Cologne's Jewish quarter, building its first synagogue by 1040 C.E. The Crusades put an end to peaceful coexistence with Christians in 1096 C.E. Despite the Archbishop's protection many Jews were killed and their synagogue destroyed.

Source: Wikipedia — History of the Jews in Cologne (CC BY-SA 4.0)