An Irish architect's concept for a new kind of gallery, in honour of a children's writer, is helping a German city come to terms with its past, writes Derek Scally.

Teaching Germans how to remember their past is, at first glance, like teaching your grandmother to suck eggs. The past bloody century has made Germans experts, some would say hostages, of their history. Now an Irish architect, Ruairí O'Brien, has won a prize for his unconventional way of helping a people remember their past.

O'Brien (41) has enlivened a tired historical debate by creating a museum honouring one of Germany's most loved authors - and now he has ambitious plans for another museum, to address the vanishing architecture of the former East Germany.

"Coming to Germany after the \ Wall came down was an opportunity to be a part of history," he says in his Dresden office. Educated at Blackrock College in Dublin, O'Brien left Ireland in the early 1980s to study architecture in London, Edinburgh and New York. He has lived in Germany since 1991, which shows in the German words and phrases that pepper his English.

"I decided that if I was looking for something new to do, for my generation it was to go to Germany."

As an architect and conceptual artist, he found himself drawn to Dresden, the architectural jewel of eastern Germany, which was largely destroyed by Allied bombers in 1945. He worked his way through a variety of projects and jobs before the chance came along to work on a museum dedicated to Erich Kästner.

Kästner is best known around the world as the author of the children's book Emil And The Detectives, but he also enjoyed huge success as a journalist, poet and screenwriter.

Kästner, who died in 1974, was a native of Dresden, but the city had no museum to honour its famous son. When O'Brien presented his plans to fill the gap, he was surprised to run into huge official opposition.

"The people from the museums authority told me that a Kästner museum would need at least three floors, as if the bigger the man, the bigger the museum needs to be," he remembers.

"There's this 19th-century idea of getting the perfect collection, of telling the whole story. But how complete is complete? Is it ever possible to tell the whole story?"

O'Brien's concept for the museum was as radical as it was modest. Instead of endless halls filled with dusty exhibits, he designed a series of drawer-filled cabinets containing multimedia exhibits. When fitted together, the cabinets take up no more space than a modest walk-in wardrobe. When opened out, the mobile museum comfortably fills a medium-size room.

The installation doesn't pretend to tell the whole story of Kästner's life. Instead it offers visitors the freedom to take in as much or as little as they want without feeling overwhelmed or guilty.

The ingenious cabinet concept lets them learn about Kästner by rifling through a stranger's drawers: always a popular, if guilty, pleasure.

O'Brien was frustrated but also challenged by the opposition and financial constraints he faced. If traditional museums are petrol-guzzling saloons, his is a one-litre runabout.

Freed of the obligations that accompany official funds, his multimedia concept presents Kästner as the modern, multimedia artist he was rather than the doting-uncle image successfully pushed into popular memory by Germany's cultural guardians.

"I call it my micromuseum concept. By working with micro fragments, we can give a better concept of the macro context," he says.

His experiences with the Erich Kästner Museum taught him a lot about Dresden's approach to dealing with its history. Rather than confront the "sweet and sour" of its past, as he calls it, Dresden, in common with other areas in Germany, shows a selective and often superficial approach. These days, distant kings and forgotten nobles have been reanimated to attract tourists while the recent past is ignored.

Nowhere is it more evident than in Dresden's obsession with reconstructing pre-1939 buildings wiped out in the war while it ignores or erases the plattenbau, prefabricated apartment blocks that sprouted up in East Germany to address the chronic housing shortage.

O'Brien believes Dresden's attempts to forget this less illustrious chapter of its architectural history will hobble its attempts to become a living, breathing city. His next museum project will tackle this historical blind spot and, though it's a long way from completion, it is has already touched a raw nerve.

Plattenbau were once a popular alternative to decrepit pre-war buildings, but now more than a million of the unloved apartments stand empty. Many authorities have begun to tear down the tower blocks that unintentionally became the socialist signature.

For O'Brien there is no better place to remember the plattenbau than the site of a Dresden factory that once churned out the huge panels for the towers. The factory, in Dresden's Johannstadt neighbourhood, closed in 1990 and has since been demolished. But O'Brien has secured a small portion of the factory site where he will display 50 tonnes of material he salvaged from the ruins.

Like the Kästner museum, the plattenbau museum will take a modular, selective approach to the material to create what O'Brien calls a historical carpet of memory.

"The broken pieces of plattenbau are fragments of reality. Seeing the pieces on the ground will allow people to see the familiar in a new way," he says.

The history of the plattenbau is not just the sorry tale of a failed housing experiment, he argues, but the story of an imperfect solution to the pressing problem of a housing shortage.

"The plattenbau are a tribute to the tenacity and pragmatism of the German spirit after the total defeat of the second World War," he says. "When you know the difficulties of the time, what was achieved is even greater in hindsight."

Nevertheless, as the Ballymun towers vanish from the Dublin skyline, O'Brien is no apologist for prefabricated tower blocks.

"Plattenbau are not beautiful. I don't want to live in one and I don't think they should all be preserved. But they shouldn't be ignored either," he says. "They are a valuable chapter in city development and part of the discussion of how and where we want to live in the future."

As well as rehabilitating the memory of the plattenbau, O'Brien hopes the project will regenerate Johannstadt, an area still suffering from the factory's closure in 1990, and help win over sceptical locals.

Across town, the scepticism about the Erich Kästner Museum has long since vanished.

O'Brien's museum began life with no public funding, no location and no exhibits. On Sunday, the little museum that could celebrates its third anniversary and Kästner's 104th birthday.

The museum has attracted more than 25,000 visitors and is even announced on trams that stop around the corner, a telling gesture from the city fathers. Another official blessing came earlier this month, when the Federal Culture Foundation presented O'Brien with an award for his micromuseum concept.

"This museum is a completely new form of biographical exhibition," writes one impressed visitor in the guest book. Another writes: "It's very interesting but takes some getting used to."

By taking an unorthodox but respectful approach to Kästner and the plattenbau, O'Brien has avoided the nostalgia trap that many Germans have fallen into. He has given the people of Dresden new ways of looking at their past and an impetus to explore new areas in the future.

• The Erich Kästner Museum's website is www.erich-kaestner-museum.de