The 500kg US explosive was found on a building site in Dusseldorf in western Germany.
It was deactivated by a bomb disposal team in the early hours of Tuesday as residents took cover in school buildings.
Emergency workers cleared a 500-metre radius as they defused the device. A railway line was blocked and the wait was prolonged by people “refusing to leave the danger area”, authorities said.
Such finds are not unusual in Germany. A British bomb was destroyed in a controlled explosion in Hamburg in the north last month.
Allies forces heavily bombed German cities and industrial heartlands in the closing stages of the war.