L to R: This Nov. 10, 1989 file photo shows Berliners singing and dancing on top of the Berlin wall to celebrate the opening of East-West German borders; (Top R) This Nov. 11, 1989 file photo shows East German border guards looking through a hole in the Berlin wall after demonstrators pulled down one segment of the wall at Brandenburg gate; (Bottom R) This Nov. 10, 1989 file photo shows East Berliners getting helping hands from West Berliners as they climb the Berlin Wall.Monday marks the 20th anniversary of the fall of the Berlin Wall.