prechteck’s design proposal for the extension to the national library of Austria located at the Hofburg in Vienna contains a number of cultural facilities, creative studios, a restaurant and shops.straddling the border of a nearby park, the project is a continuous spiral form that houses its 1200sqm core exhibition hall and a smaller 600sqm multifunctional hall underground.pulling up out of the urban landscape, the extension features a mosaic form of crystal-like excisions along its body, allowing natural daylight to filter through to the interior. public circulation on the street level is not damaged by the extension, which arches off the ground to create a curvilinear roof garden on its roof. drop-off and fire emergency line is placed under the arch, allowing cars to drive under the structure to access the main entrance.all of the mentioned facilities are housed in one seamless structure, creating at each point a different spatial experience towards the Hofburg and directs its visitors intuitively to the foyer and into its programs.