Cologne ordered the evacuation of 20,000 residents on Wednesday after an American bomb from World War II was found in the riverbed of the Rhine.
The New York Times reported that it took roughly 30 minutes for technicians to defuse the 440-pound bomb, and that residents were soon allowed back into the half-mile radius around the Muelheim Bridge where the bomb was found.
The evacuation was the largest the city's seen since the end of the war 70 years ago, however it's not uncommon for Germans to find the explosives during excavations and construction projects.
In May alone, Germans found over a half-dozen bombs in rivers, lakes, and shallow ground.
"It is an issue in most major German cities, where anywhere from 5,000 to 10,000 unexploded bombs are believed to be lying under the ground," said Sebastian Dosdall, the head of a company that clears old munitions. "It is a problem that will not be solved easily. It will be with us for quite a while yet."
Older Germans like Johanna Klaes, 86, have said that the evacuations bring back memories of the war and the country's Nazi years. The memories are often unpleasant, prompting memories of Allied bombing raids.