A large-scale evacuation has begun in central Berlin so that experts can defuse a World War Two bomb.
The evacuation affects about 10,000 people and the zone includes homes, government ministries and museums.
The operation is causing severe transport disruption, with trains unable to stop at the city’s main railway station.
The 500kg (1,100lb) bomb, thought to be made in Britain, was found during construction work in Heidestrasse.
Buildings are being cleared in an 800m (2,625ft) radius around the site.
Berlin’s famous Charité university hospital and a military hospital have been partly shut down.
Berlin police tweeted a photo of their bomb disposal team at the scene, poised to defuse “the source of all the evil”.
Thousands of unexploded bombs from the 1939-45 war are found every year. The Berlin bomb was found last Wednesday.
Last September about 65,000 people were evacuated in Frankfurt because of an unexploded bomb.
Rail company Deutsche Bahn and other transport operators have warned of large-scale disruption for trains, trams and buses in the area.
Flights to and from Tegel airport – about 7km (4.5 miles) away – will not be affected, authorities said on Thursday, although planes coming in to land will avoid flying over the site.
Tegel, which is Berlin’s busiest airport, was briefly closed last August after the discovery of a Russian World War Two bomb.
Relics of Germany’s darkest hour
By Jenny Hill, BBC Berlin correspondent
Sitting in the warm sunshine, suitcases beside them, Gabrielle and her sister gazed at the police cordon stretched across the glass façade of Berlin’s main railway station. “I hope it doesn’t go off!” she laughed.
Like many Germans, Gabrielle was rather sanguine about the presence of unexploded ordnance. “They defuse World War Two bombs from time to time in Osnabrück – my home town – too,” she added.
The relics of Germany’s darkest hour turn up with surprising regularity. Estimates vary, but it is thought that at least one in every 10 Allied bombs dropped on this country during World War Two failed to detonate.
They are discovered so frequently, often by builders or farmers, that every German state has a specialist team responsible for their disposal. But rarely do they cause such widespread disruption.
Other WW2 bombs discovered in Germany
- May 2017: 50,000 people were evacuated from Hannover while three British-made bombs were defused
- December 2016: More than 50,000 evacuated in Augsburg over 1.8-tonne British explosive
- 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 – half the total population – after two bombs were found in the riverbed of the Rhine
- June 2010: Three members of a bomb disposal squad were killed in Göttingen during an operation to defuse a bomb found on a building site