German authorities were evacuating around 50,000 people from their homes in the northern city of Hannover while five suspected aerial bombs from were made safe for removal.
City officials said two suspected bombs were found at a construction site and three more nearby. Leaflets in German, Polish, Turkish, English and Russian were delivered door-to-door to make sure everyone evacuated on Sunday.
The city's museums were open for free and the senior citizen's agency organized an afternoon Scrabble and card-playing gathering so evacuated residents would have places to go.
Authorities said they hope people will be able to return to their homes by evening.
Germany was heavily bombed by Allied planes during the war and such finds are common. In December, more than 54,000 people in the southern German city of Augsburg had to while authorities defused a giant 1.8-ton aerial World War II bomb.