A building for housing an ordered collection of items-for example, a library, archive, or patent office-places the items along a spiral arm (1), and makes the items easily movable with wheeled cases, so that the collection can grow. Preferably the spiral is housed in a spiral building arm starting at a central building (2) and winding outward, with interconnecting legs (2) providing access to the far reaches of the arm. The building never becomes too small because the end (E) of the building can be extended gradually. As the collection grows, the cases are merely pushed along to make room as needed. The collection never gets out of order.