Gordon Brown, the British prime minister, Nicolas Sarkozy, the French president, Dmitry Medvedev, his Russian counterpart, and Hillary Clinton, the US secretary of state, are due to attend the celebrations hosted by Angela Merkel, the German chancellor.
Thousands of tourists have poured into Berlin to mark the event on November 9, 1989, which led to the reunification of Germany, the collapse of the so-called "Iron Curtain" and the end of the Soviet Union.
Merkel, who was working as a scientific researcher in East Berlin at the time, said on the weekend that the fall of the wall was "the happiest day in recent Germany history".
Al Jazeera's David Chater, reporting from Berlin, said there was a real sense of celebration in the air.
"But it is nothing like that feeling on the streets on that day in particular, because it marked the end of communism itself."
Celebrations are planned all over the city, including the toppling of 1,000 giant, brightly coloured dominoes along a 1.5km stretch of the wall's original path.
But for some German residents, the 1990 reunification of the country remains a sore point.
On Saturday, several hundred leftist demonstrators protested against the planned celebrations in Berlin.
A poll of more than 1,000 Germans carried out for the Leipziger Volkszeitung newspaper showed one in eight wanted the wall rebuilt - with the numbers nearly equal in the eastern and western parts of the now-unified country.
Shaken by the mass flight of its citizens into capitalist West Berlin, East Germany began erecting its "anti-fascist protection barrier" in the early hours of August 13, 1961.
According to a study published this year, at least 136 people were killed at the Berlin Wall between 1961 and 1989 while trying to escape.
However, thousands managed to evade the minefields, dogs and guards in watchtowers, using schemes including tunnels, aerial wires and hidden compartments in cars in order to make it to the West.