It was only a few years since he had been released from an East German prison, serving time for multiple attempts to cross into the West. He was forbidden from going back East to visit his family.

"Late in the evening a guy came in [to the bar] and shouted: 'The wall is open, the wall is open'," Mr Juritza recalls. "I said to him: 'Dream on and don't drink so much beer'."

Then he went home and went to bed. Even when he found out the next morning it was true, it was almost two months before he dared venture back over the border.

Now he works as a tour guide in Berlin, telling tourists and locals about the East Berlin he knew, that is gradually fading into the background of modern Germany. He is adamant that these stories must not be forgotten.

"The story of people who tried to escaped, who were shot at the wall or went to prison because of their opinion is absolutely necessary to be told, just like the evils of the Stasi," he says. "Otherwise these stories would be buried to oblivion. And how to learn from history if history is forgotten?"

The wall was a physical object, strung across and around West Berlin by the paranoid despots of the German Democratic Republic. It sliced the city overground and under: bricked-up "ghost stations" dotted the subway, pressure plates,  "light traps" and barbed wire filled the tunnels under Berlin.

The images of the wall's fall, "Mauerfall", are a touchstone of the 20th century. But it was the end of a sharp psychological divide, too – not just the dismantling of a roadblock, it marked the demise of one of the most sinister, manipulative surveillance states the world has known.

At the old Stasi (state security) HQ in East Berlin, tour guide Franziska Kelch improvises a chilling reconstruction of an interrogator's monologue.

Her group sits in simple chairs perched on the daggy linoleum, in the plain, beige-wallpapered banality of a room that smells of the 1960s and fear.

Smiling and casual, in a blue coat and grey scarf, Ms Kelch warns her "prisoner" that his wife may not wait for him to confess, that his children are growing up without him, that she has all the time in the world to wait until he admits to his thought crimes against socialism.

If he does not, freely and generously, confess to all the crimes he can imagine, he will spend more weeks, more months in his cell, alone, in an environment meticulously designed to break him by psychologists armed with a thick file on his life, refined by spies and informants to incredible detail.

Ms Kelch was a West German 8-year-old when the wall came down. That moment had no immediate memorable impact on her life at all.

But later, at school, she met a girl whose parents fled East Germany before the wall came down. Gradually, as she grew up, she learnt the stories of the oppression that lived so close to her home.

A friend's father, from East Germany, went to the old Stasi archives, and discovered his neighbour had spied on him in the 1970s.

"He wrote reports [for the Stasi] about what he was doing, what he looked like," Ms Kelch said. "He wrote that he was sometimes drunk, that he changed girlfriends quite a bit, that he liked Western clothing and had long hair.

"This was the normal life of a man in his 20s."

But in East Germany, it was enough to mark you as a potential enemy of the state.

A quarter of a century ago, the barriers between east and west fell.

"I had never seen such euphoria," said the border guard who opened the first crossing in Berlin.

This weekend the euphoria will be remembered with a "Lichtgrenze" – an installation of 8000 helium balloons lit from within, lining  a 13-kilometre stretch of the former Berlin wall. At 11pm on November 9 they will float into the air as the Berlin State Opera orchestra plays Beethoven's Ninth at the Brandenburg Gate – an ode to joy.

"It is a good symbol for not forgetting, an event, that everybody will remember.," says Mr Juritza. "Of course the Lichtgrenze cannot reflect what the wall was. But it is a chance for younger people to be part of the remembrance of the event."

Ms Kelch says during Lichtgrenze she will remember all the images and stories of the wall, and what it represented, that were drummed into her as she grew up, and that she has heard from her fellow tour guides, many of whom were imprisoned, tortured, interrogated and broken within the grey building they now show to curious tourists and rowdy schoolchildren.

"I know that I am going to see this footage of people crossing at the checkpoints into West Berlin and when I see that I still get goosebumps and I still have to cry sometimes," Ms Kelch says. "These lighted balloons … they turn this ugly, grey, depressing thing into a chain of light. When I walk past it Sunday evening that will definitely be emotional."