Known to locals by its Slovene acronym NUK, the library was originally established by Empress Maria Theresa in 1774 and moved to its current Plečnik-designed building in 1941. Aside from serving as one of the country's central educational and cultural institutions it's also considered one of the prolific architect's most monumental works, and is a must see for visitors to Ljubljana. Highlights include the somewhat schizophrenic brick and stone façade, the colonnaded central staircase and the massive main reading room. A planned expansion on nearby Zoisova Cesta has been in the works for nearly 20 years, but has been plagued by a host of problems, most notably caused by the discovery of Roman ruins, which is a surprisingly common occurrence in and around the city.