Earlier, Chancellor Angela Merkel said the fall of the wall had shown the world that dreams could come true.
Tens of thousands of people attended events, including a "citizen's party" at the Brandenburg Gate.
The Berlin Wall was built in 1961 to stop people fleeing the communist East.
Its fall in 1989 became a powerful symbol of the end of the Cold War.
The wall stretched for 155km (96 miles) through Berlin but today only about three kilometres of it still stands.
At least 138 people died trying to flee to West Berlin.
Within a year of the wall's collapse, Germany - divided after its defeat in World War Two - was reunited.