Congress authorized the United States Holocaust Memorial Museum in 1980 to be a permanent living memorial to all victims who perished in the Holocaust. The building has been designed as a living institution dedicated to research and teaching as well as to contemplation and commemoration. The Museum building houses permanent and temporary exhibition spaces, a research library and archives, two theaters, interactive computer learning center, classrooms, a memorial space. Architect James Ingo Freed created a relationship between the museum building and the exhibitions within. To develop his design, he visited a number of Holocaust sites, including camps and ghettos, to examine structures and materials. The result is not a neutral shell. Instead, the architecture, by a collection of abstract forms — invented and drawn from memory — refers to the history the museum addresses. Architectural allusions to the Holocaust are not specific. Visitors make their own interpretations. The subtle metaphors and symbolic reminiscences of history are vehicles for thought and introspection. The curved portico of the 14th Street entrance — with its squared arches, window grating, and cubed lights — is a mere facade, a fake screen that actually opens to the sky, deliberately hiding the disturbing architecture of skewed lines and hard surfaces of the real entrance that lies behind it. In Freed's words, "Visitors must pass through the limestone partition to enter a concrete world." This motif of contrasting appearance and reality is repeated throughout. Along the north brick walls, a different perspective reveals a roofline profile of camp guard towers, a procession of sentry boxes. Above the western entrance, a limestone mantle holds a solitary window containing 16 solid "panes," framed by clear glass, reversing the normal order and obscuring the ability to look in or out. I’ve seen a few different souvenir replica buildings of the Holocaust Museum. A hard-to-find metal version was commissioned in 2005 and produced by InFocusTech. Others have been made of plaster and a "bonded marble" (resin by any other name) was produced in 2002, but may not be available in the gift shop now.