Located in Metlika Castle, the Bela Krajina Museum's small collection is an eclectic grab bag of minor finds from local archaeological sites (Iron Age and Roman era) and ethnographic displays relating to art, craft and village life as well as a room dedicated to Bela Krajina's role in WWII. It's all pepped up somewhat by audio soundtracks that blast out with startling velocity when you step close to some exhibits.
There's also a 20-minute film (in four languages) introducing Bela Krajina.