The oldest museum in Croatia, the Museum of Slavonia is housed in the renovated city-guard building with a glass dome over an arcaded patio. It showcases Slavonian history through the ages. Start on the 2nd floor with the Neolithic section and work your way down. Exhibits – gorgeous anthropomorphic figurines, burial goods, ceramics, metalware – are thoughtfully curated and, except for the last few rooms on the 1st floor, displays have English explanations.
Afterwards, hop across the square to the museum's second building, housed in Osijek's old Magistrates building. The ground floor here is home to the Lapidarium, with plenty of Roman stelae and tombs, and the 1st floor hosts exhibits on Trvđa's history as well as temporary exhibitions.