The historical building from the architects Rittmeyer & Furrer from 1914 houses the three institutions of library, natural science collection and art museum. After a temporary addition for museum functions could be constructed with private means, an expansion for library usage is to take place, as well.
The project attempts to change as little as possible the historical building in its external appearance as well as in its interior. Thus, the façades are not affected and the existing exterior court, which serves to provide light and air, will not be transformed into an air-conditioned interior space. The main part of the library expansion—the new lending room, the new reading room and the study library—are found on those parts of the parcel not covered by the existing building.
The addition, which must make do with three leftover areas around and in the existing building, finds its own identity and ordering principle by virtue of the way in which it presents itself outwardly as an underground building with skylight volumes. With these elements, the new building is able to enter not just into a usage-based relationship, but more so into a precise architectonic relationship with the historical building. The composition of the intersecting, longitudinal stone volumes of the Rittmeyer & Furrer building is expanded and complemented by the translucent, glass skylight volumes of the new building.
During the day, the skylight volumes appear as large, white-glowing, glass volumes, while appearing as powerful, glowing lanterns at night.
The skylight volumes are developed out of the column/level structure of the sunken building volumes and grow towards the light as pure skeleton structures. In the interior of the building, they form those rooms that are foreseen for intense, individual work and for the public: the reading and periodicals room, the study rooms and the lending and entrance area in the courtyard.
The project follows the ideal type of a library space: large, extra-high rooms with skylights, in which people spend time in the anonymous collective, while yet alone in singular concentration upon the object of their study. The structure of the load-bearing construction forms a delicate space division for the virtual separation of the visitors.
Attention is called to the three institutions by means of a large-format sign made with metal letters that is placed as a powerful piece of inlay work into the flooring of the forecourt and into the roofing surface of the new building, respectively. The large, inlaid typography, over which one walks and upon which one stands, refers through and beyond its signage function to the "deeper meaning" of the ground under the visitor's feet.
The common entrance to the three institutions through the portico is left unchanged, allowing the wonderful staircase from Rittmeyer & Furrer to be left almost entirely intact. A new staircase descending to the new main floor of the library supplements the existing main staircase that connects the three institutions today.