Bomb squad technicians defused the three American explosives, two weighing 1,000kg and one 500kg, at 7:19pm (1719 GMT) on Wednesday, having earlier set up an evacuation zone of about 10,000 square metres for 12 hours.
Road and train lines were closed throughout the day, and city officials went door to door, vacating about 20,000 people from their homes and closing 58 hotels as well as numerous restaurants and businesses.
The heart of the city was left deserted, with a hospital, two old people’s homes, nine schools and a TV studio evacuated.
Weddings had to be relocated from Cologne’s town hall, and a man was taken into custody after trying to break through a barrier and enter the zone, local authorities said.
The bombs had been found during building work on Monday in the Deutz area on the east bank of the River Rhine.
German construction sites have regularly unearthed unexploded World War II ordnance.
In Frankfurt, the discovery of a 1.4-tonne bomb in 2017 led to the removal of 65,000 people, the biggest such evacuation in Europe since 1945.
In 2021, four people were injured when a World War II bomb exploded at a building site near Munich’s main railway station, scattering debris over hundreds of metres. (AFP)