Story highlights The bomb squad says the device could have blown a crater 10 feet deep

Experts successfully defuse a 220-pound bomb near Berlin's main train station

"Here in Berlin it is a fact of daily life to defuse bombs," a police spokesman says

Many World War II-era bombs remain undiscovered in Berlin and other cities

It happens more often than you might think: Streets cordoned off and bomb disposal experts called in to deal with unexploded bombs that were dropped on Germany nearly 70 years ago.

Commuters in Berlin Wednesday were the latest to suffer the inconvenience of dealing with ordnance dating back to World War II.

This time the culprit was a Russian-made aerial bomb weighing in at 100 kilograms (220 pounds), unearthed just two meters away from a train track leading into the city's main train station.

Nearly 840 people were evacuated from the central Berlin area, police said, before bomb disposal experts moved in to defuse the device.

About 25 minutes after they started their delicate task, the mechanical fuse was unscrewed and the bomb was disabled.

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Alert over, Berliners could return home and go back to their everyday business.

A member of the bomb disposal team told CNN the bomb could have blown a crater 3 to 4 meters wide and 3 meters (10 feet) deep, had it gone off.

The device was discovered by Heidestrasse, a lightly populated street with an industrial feel in the former "no man's land" between East Berlin and West Berlin.

"They do risk a lot, but they have a lot of experience," Berlin police spokesman Jens Berger told CNN as the bomb disposal team set to work.

"Here in Berlin it is a fact of daily life to defuse bombs, but without question they are risking a lot."

Wednesday's operation was made more complicated because there was a depot for freight trains on one side of the site and houses on the other, Berger said.

The device was found Tuesday afternoon by a bomb disposal team that was checking out a construction site near the Hauptbahnhof, the central station.

Roads were closed in the area overnight as the experts assessed the best way to deal with the device. Some train services were delayed Wednesday, said Holger Auferkamp, spokesman for national railway operator Deutsche Bahn, but Berlin's metro system, or S-Bahn, was not affected.

It may seem surprising that unexploded bombs remain undiscovered in Berlin and other German cities decades after World War II ended. But so many were dropped by Allied forces during the war that finding them all will still take years.

Their presence is sufficiently common that private bomb disposal teams are contracted by German railway operator Deutsche Bahn and other companies to check that sites are safe when building works are planned.

Some bigger devices have been found elsewhere.

A 250-kilogram (550-pound) bomb discovered in central Munich last August had to be detonated where it lay because the fuse was unstable. The explosion damaged nearby buildings.

In 2011, 45,000 residents were evacuated from the city of Koblenz, situated on the Rhine and Moselle rivers, as bomb squads dealt with two bombs and a military fog-producing device that were dropped by American and British warplanes in the last years of the war.

One was a 1.8-metric ton British air bomb that could have wiped out the city center, according to the local fire brigade.

They were exposed 65 years after being dropped when water levels in the Rhine River fell to record lows, prompting what officials said was the biggest evacuation since the war's end.

Sometimes the bombs can have a more deadly impact.

Three members of a bomb-disposal squad were killed in 2010 when the device they were trying to defuse in the German town Gottingen went off.