The Moses Mendelssohn Foundation is planning an extension to the Behrend Lehmann Museum in Halberstadt. At first it seems contradictory not to develop this public building directly from the street. The design plays with this contradiction by keeping itself closed in cubature, facade and materiality on the street side. Only a wedge-shaped incision in the edge of the block allows a view of its, historical garden core and divides the building into two. A pool, however, prevents the passage between the two parts and thus the curious passer-by must go through the nearby historical gate. When one enters the extension building, all rooms can be easily reached through the central staircase. Alternatively, an circulation sculpture is available for the youngsters, which offers a completely different experience of the same rooms.