Bomb find prompts Cologne's biggest evacuation

The BBC has an article about a little leftover, if dangerous, history:

Some twenty thousand people in the German city of Cologne have been forced to leave their homes as authorities defuse a one-ton bomb from World War Two. Schools and kindergartens as well as the zoo remained closed during the city's largest post-war evacuation. About eleven hundred residents of a retirement and disability center in the Riehl area were among those taken to safety.
It is not unusual for unexploded bombs to be discovered in Germany. Allied bombers frequently targeted Cologne in World War Two.
The deactivation of the one-ton device, which was found near the Muelheim bridge crossing the Rhine river, was planned for Wednesday afternoon.
City officials said in a statement that, during this time, the river would be closed for shipping and the airspace would also be closed.
The bomb was found during preparations for the construction of a pipeline, according to local media. It is believed to be an American design and was buried five meters underground. A one-kilometer exclusion zone was set up around the spot where the device was found.
Otto Ludorff, the head of the care home affected, said the evacuation placed a "physical and emotional burden" on its residents, whose average age was 86, according to a German news channel.
Cologne was a regular target for Allied bombers during World War Two.
Hundreds of tons of unexploded ordnance are discovered in Germany every year.
The explosives are usually defused safely though, in 2010, three bomb-disposal officers were killed during an attempt to make a bomb safe.
In December of 2011, the biggest bomb disposal operation in Germany since 1945 was mounted in Koblenz to defuse two bombs from World War Two found in the riverbed of the Rhine.

Rico says we dropped a lot of stuff on Germany...