On November 9, 1989, the Berlin Wall fell. Or, to be more precise, the border guards opened the gates and allowed crowds from East Berlin to cross into the west. People celebrated by climbing onto the wall and dancing.
The fall of the wall was widely seen as a victory for freedom. But things are not that simple.
In the three decades since 1989, new walls have gone up, and existing walls and other barriers to the free movement of people have been strengthened, in many parts of the world.