Collections of the Ptuj – Ormož Regional Museum are on display at various locations.
The castle houses the following collections: a collection of musical instruments, a collection of weapons, a collection of feudal domestic culture, a collection of turquerie, a collection of carnival masks, a collection of paintings on glass, the castle gallery, the Marko Sluga collection and the France Mihelič graphic cabinet.
The former Dominican monastery is devoted to to archaeology, with an ancient, medieval and modern lapidarium, a reconstruction of Mithraea II and V, a collection of small archaeological finds and a numismatic collection.
On the right bank of the Drava there are Mithraea I and III, sanctuaries from the 2nd and 3rd centuries.
In the building of the former town prison in Prešernova ulica is the historical collection Ptuj and its Surroundings in the 20th Century, the Mihelič Gallery is devoted to exhibitions of contemporary fine art.