The gallery occupies a complex of three connected buildings: the 1896 neo-Renaissance National House (Narodni dom), a 1993 modernist wing by architect Edvard Ravnikar, and a 2001 glass atrium linking both sections. After a four-year renovation, all three wings opened as a single circuit for the first time in 2016. The National House features ornate ceilings and natural-light-filled halls.
The permanent collection is arranged chronologically: medieval sacred art, Baroque works (Gregorio Lazzarini, Giulio Quaglio), Biedermeier portraits by Jožef Tominc, neoclassical paintings by Franc Kavčič, Realists Janez and Jurij Šubic, Impressionists Ivan Grohar, Rihard Jakopič, Matija Jama, and works by Ivana Kobilca – the first Slovenian woman painter of European stature. The glass atrium houses the original Robba Fountain (Fountain of Three Carniolan Rivers, 18th century) – its replica stands outside the Town Hall in the Old Town.
A separate room is dedicated to Zoran Mušič (1909–2005), one of Europe's leading modernists. Temporary exhibitions rotate every 3–4 months. The ground floor has a café with a terrace overlooking Tivoli Park, a gallery shop, and Gal's Room for children's workshops on Saturdays.