Around 21,000 people had to leave the area in Koblenz as the 500-kilogramme (1,100-pound) bomb was successfully defused, before the fire brigade allowed residents to return to their homes.
The operation came a day before three times as many people must leave their homes in Frankfurt to allow for a Royal Air Force bomb to be neutralised, in the biggest evacuation of its kind in postwar Germany.
The city said police will enforce a 1,500-metre radius evacuation zone starting early tomorrow and residents will probably need to stay away until 8:00 pm (1800 GMT).
Seven decades after the end of the Second World War, unexploded bombs from intense Allied raids on Nazi Germany are still occasionally found in building sites, forests and fields and sometimes even in private gardens.