More than 26,000 people had to clear out from their residences on Sunday as demolition experts began removing a 1.8-ton bomb left over from World War II, discovered in March in a garden in the western German city of Paderborn.
The work to defuse the British bomb meant that buildings within a 1.5-kilometre radius had to be evacuated.
That meant getting people out of two hospitals, several homes for the elderly, the university and parts of the historic old town.
Patients in two further hospitals had to be moved to more secure parts of those facilities.
More than 1,000 volunteers helped fire crews, police and emergency services make sure that all residents were clear of the danger zone by noon (1000 GMT).
Emergency shelters were also set up.
The bomb was discovered a week and a half ago during construction work in a garden.
It was buried only 80 centimetres deep, meaning it could cause significant destruction if it goes off.