In the capital, tens of thousands of people watched a massive-scale street performance featuring a pair of giant marionettes suspended by cranes marching slowly through downtown.
Wearing a green dress, the 7.5-meter (25-foot) "small giant" wandered one route looking for her partner _ a 15-meter (50-foot) "big giant."
The big giant, clad as a deep-sea diver, was pulled by a crane from under the waters of the Spree river outside Berlin's main train station, then paraded past the federal Chancellory building along his route.
The spectacle, performed by France's Royale de Luxe theater company, was to wind up with the two finding each other at the landmark Brandenburg Gate _ reuniting on the former dividing line between East and West Germany.
The two nations were separated for more than four decades until the fall of the Berlin Wall in 1989 and official reunification in 1990.
In a speech in the southwestern city of Saarbruecken, newly-reelected Chancellor Angela Merkel reminded a crowd of about 1,000 people that German unity had not just "fallen from the sky" but was the result of years of "courage and determination." She said Germans need to keep this in mind when faced with issues like the current economic crisis or other global problems.
"Freedom and responsibility go together," she said.
The events in Saarbruecken, held there according to the tradition that the official Unity Day commemorations are held in the hometown of the president of parliament's upper house, started with a church service attended by Merkel and other top politicians.
Security was tight for all events, following a series of extremist videos recently posted on the Internet that mentioned Germany directly, but no incidents were reported.
The videos, released before Sept. 27's national election, made references to jihad, or holy war, and retribution against Germany, but did not mention any specific threats.