The bomb was defused by a team of five police specialists, and it was transported to an area outside of town before being destroyed in a controlled explosion.
A number of buildings, including the Central Railway Station, Economy Ministry, Federal Intelligence Service (BND), and the Indonesia and Uzbekistan Embassies, were also evacuated.
The British bomb has been removed, the main railway station has reopened and traffic is getting back to normal.
By Friday afternoon however it was reported that Berlin's main train station had opened again. The police cordon has now been lifted.
It was unclear how long the bomb disposal squad would take to disable the bomb found during construction work on Heidestrasse in the district of Mitte.
The 1,100lb bomb was believed to have been dropped by the British. Before the bomb disposal experts move in, police will go house to house to check the zone has been completely cleared. More than 70 years after the end of World War II, it is not uncommon for unexploded bombs to be in this way in Germany.
Flights from Berlin's Tegel airport are not affected but passengers have been warned that public transport to the city's two airports - Tegel and Schoenefeld - would be disrupted. Many thousands of residents and employees will have to stay clear of, or leave the area by 9:00 am local time (0700 GMT), and not return until the bomb is safely defused.
Such finds are also common elsewhere in Europe, and Slovak authorities on Friday had to evacuate people in a town near the southern border with Hungary after four unexploded World War II bombs were found by a man walking his dog.