Standing on the approach path to the museum entrance - flanked with railway lines, as a memory of the deportation - Libeskind remarks: "Nussbaum was an amazing character. Even in those catastrophic circumstances, he believed that his works would communicate to a future. He didn't make it - but I think he really believed that he would make it, that somehow, through his creative work, his paintings, he would be redeemed. But he wasn't. He was on the last deportation train to Auschwitz in late 1944. His work was a message in a bottle, thrown into the ocean."

By then almost forgotten, his paintings were rediscovered in storage in Belgium after the war. The surviving members of the Nussbaum family began to bring them back to Osnabruck in 1970 - since when there have been several exhibitions there and in cities around the world. Public subscription helped to safeguard them in the early years, and now the Nussbaum collection is officially designated and protected as nationally important by the state. One picture in particular - a self-portrait of 1943 with Jewish identification card and Star of David - became a powerful symbol of the period and is frequently reproduced in German schoolbooks. But the building of the museum in Osnabruck is the completion of the process: Nussbaum has finally come home.

The building is an answer to those critics who regard Libeskind's work as being either unbuildable or unduly assertive. They look that way in the drawings and models, but in real life a curious transformation overcomes them: both the Jewish Museum in Berlin, and this one in Osnabruck, are positively self-effacing. You can wander past and almost not notice them. The Nussbaum Museum is composed of three intersecting parts, the geometry dictated by their alignment with former Jewish centres in the city such as the now-vanished synagogue. The different sections are clad respectively in oak, smooth concrete and zinc, and the whole composition sits quietly in the garden, surrounded by sunflowers, behind an existing 19th century gallery. It is right next door to the building that once housed the city's Nazi headquarters, where atrocities took place.

Libeskind seems more amused than annoyed at the way his buildings are habitually misread when they are at the planning stage. "I remember early on, people were saying that the building would be very aggressive, very difficult. I said, don't worry, you will hardly notice it. And it's like that, there's a blankness to it. The city wants me to erect a big sign, but I say no. Part of the idea is that it is stepped back, that you discover it."