Following the end of World War II, a venue was needed to house the legislature of Slovenia, at the time a federal republic of communist Yugoslavia.

Due to the centralizing policies of the pre-1941 Kingdom of Yugoslavia, there had been no sub-national legislatures in the interbellum period; the Austro-Hungarian palace on Congress Square that had housed the pre-1918 Provincial Diet of the Duchy of Carniola did still exist, but had been repurposed as the rectorate of the University of Ljubljana, and additionally had an undesirable association with foreign rule.

Two designs were submitted by Slovenia's most respected architect, Jože Plečnik; the second of these, known as the "Cathedral of Freedom," featured a tall cone-shaped dome rising to 394 ft (120 m) atop a double colonnade.

[3] The authorities rejected Plečnik's designs as too ostentatious, and instead commissioned the architect Vinko Glanz [sl], who had proposed a much more conservative and modest design than either of the Plečnik concepts: an austere modernist palace in the International Style, with no monumental elements or decorations save a large sculptural group of bronze figures framing its main portico.

A freestanding cube,[6] the main façade faces Republic Square and is inlaid with Karst marble, with green Oplotnica granite below each window.

The largest, a 67.4 by 1.4 metres (221.1 by 4.6 ft)[5] wall painting by the 20th century mural artist Slavko Pengov, extends across the length of the entrance hall and illustrates the history of Slovenians.

Each seat has a microphone, an automatic voting system, plug socket and access to the National Assembly's computer network.