The library consists of an external shell and an internal core. The shell follows the scale of the existing block development, the real estate offices and the old building on Ritterstraße; the core rising from the shell relates to the Stephanskirche. The materials employed are selected in accordance with this architectural concept: the shell is rough, made of stone with slate roofing whereas the material of the core is smoother, coated and with a copper roofing, and suggestive of its relation to the church.