More than 50,000 residents from the German city of Augsburg were evacuated from their homes so that a huge World War II bomb could be defused.
It was the country's biggest evacuation for an unexploded bomb since the end of the war.
The 1.8-tonne British explosive is thought to have come from a 1944 air raid, which destroyed the old town.
German police later announced that the bomb had been made safe.
Officials chose Christmas Day for the evacuation because it was less difficult than on a normal working day.
The bomb was uncovered during construction work on Tuesday.
Augsburg mayor Kurt Gribi, speaking in a video posted on the city's Twitter account as the evacuation began, called for "each person to verify that their relatives, parents and friends have found places to stay outside the [security] zone ... Look out for one another."
The authorities were confident that most people affected could stay with friends or family, but a number of schools and sports halls were opened as shelters for those in need.
Most Germans celebrating Christmas open their presents and have their main festive meal on 24 December, rather than Christmas Day.