Closed for several years following the war, the 18th-century Eltz Palace reopened in 2014 as this brilliant museum. Head up the stairs to the 1st floor for a whirlwind tour of Slavonian history, from mammoth fossils through to Bronze Age horde finds and burial goods unearthed from the medieval Bijelo Brdo culture, all the way up to the mid-20th century. On the 2nd floor a moving video exhibit plays footage of the siege of Vukovar and the town's destruction.
All the displays are well curated and have English explanations. You can also take a guided tour in English (100KN).