The National University Library is considered one of the greatest achievements by Plecnik. Its size and shape echo the example of the Prince's Palace, which stood on the same site. Plecnik project encountered resistance by the Yugoslavian authorities which were based in Belgrade. However, persistent student protests and demonstrations have been effective, and the new building was erected between 1936 and 1941. The library building is the most monumental of Plecnik's works in Slovenia. In its size and form, it models the former building "Knezji dvorec", which was at the same location and was destroyed in the 1895 earthquake. The library keeps a copy of each publication published in Slovenia. They have been significant problems with a lack of space and a new modern building has been planned to be built in the vicinity by winners of the competition Bevk Perovic.

The Temple of Knowledge

Rustic stone inserts in the smooth brick surface form a graphic tactile impression on the facade. Some of the inserted stones are archaeological remnants of the previous building occupying the site. It was modelled like the Italian palazzo, similar to the house of the Italian architect Federico Zuccari. The roof of a Greek temple is indicated by a decorative band above the smooth attic frieze. Two large vertical windows on both sides of the reading room create an interruption in the unified surface of the facade and reveal the inner structure of the building.

Plecnik saw the library as "a temple of knowledge", so he designed similar ceremonial entrance to the reading room as in his sacral building. This entrance is is an ascent from the dim obscurity of the first floor where he talks about ignorance, toward the light of knowledge. The staircase ends in a hall of the black 32 marble columns that is the vestibule to the reading room. In contrast to the monumental staircase, the reading room itself, situated transversely to the entrance axis, is a light and functional space. Its furnishing derives from the industrial aesthetics of the 19th century. There are side staircases with landings designed as balconies.

Surfaces and Details

The building and its details are replete with Gottfried Semper's theories of surfaces and the transformation of materials. Plecnik placed a statue of Moses by Lojze Dolinar above the side entrance. The handles of the main door end with a little head of Pegasus. The cellar was renovated in 2000 by Marko Music, when the building was also additionally protected against earthquakes.