Around 50,000 people in Hannover will be evacuated from their homes on Sunday while experts defuse five World War Two bombs.
The operation is the second largest of its kind carried out in Germany, and will affect around a tenth of the city’s population.
The buildings set to be evacuated include seven care homes, a clinic, and a Continental tyre plant.
Officials hope those affected will be able to return home by the evening.
The evacuations will begin at 09:00 (07:00 GMT) and residents have been advised to take necessary items like medication with them when they leave, as well as turning off gas and electrical appliances.
Rail travel may also be hit by delays after early afternoon, The Local reported.
The city has set up a programme of museum tours, children’s films, and sporting events to help those being evacuated spend the day as pleasantly as possible.
Tens of thousands of soup portions are also being prepared, according to the German news agency DPA.
Allied planes bombed Hannover heavily during World War Two, killing thousands and destroying much of the city.
On 9 October 1943, an especially deadly night, 1,245 people were killed and 250,000 left homeless by 261,000 bombs.
The largest bomb-related evacuation since the war happened on Christmas Day last year, in Augsburg.
Some 54,000 people were evacuated after a 3.8 tonne bomb was unearthed during building work.
Other WW2 bombs recently discovered in Germany
- May 2015: 20,000 people in Cologne forced to leave their homes after a one-tonne bomb was discovered
- January 2012: A construction worker was killed when his digger hit an unexploded bomb in Euskirchen.
- December 2011: 45,000 people were evacuated from Koblenz after two bombs were found in the riverbed of the Rhine. It took three hours to make them both safe.
- June 2010: Three members of a bomb disposal squad were killed in Goettingen during an operation to defuse a bomb found on a building site.
50,000 face evacuation in Hannover over World War Two bombs