Germany has commemorated the building 50 years ago of the first stages of the Berlin Wall.
For 28 years the barrier separated the communist East German sector of Berlin from the West German area.
A minute's silence was held in the city on Saturday in memory of those shot by East German border guards while trying to escape over the wall, the BBC reports.
A ceremony was held at a chapel on on Bernauer Strasse, the steet famously divided by the Wall and now site of a memorial.
Berlin Mayor Klaus Wowereit said the capital was remembering the saddest day in its recent history.
Germany's president, Christian Wulff, said the country had been securely established as a reunified country.
He said the world situation, of which the wall was a symbol, seemed irreversible to many people, but it was not the case. "In the end, freedom is unconquerable," he said.
Soldiers from the East began construction on the morning of 13 August 1961.
Initially a barbed wire fence, it became a wall which spread for nearly 160 kilometres.
More than 300 watchtowers were erected to spot escapees and minefields were laid in some sectors.
The number of people who died trying to cross the Wall is disputed, the BBC reports. At least 136 are known to have been killed but victims' groups say the true number is more than 700.