In Istria, head for Beram, a hamlet of 200 souls where the Church of St Mary on Škriljinah has an amazing fresco of the Danse Macabre dating from 1747. At Bale, a picturesque little inland town that Casanova is said to have visited, in the Ulika gallery you can see dinosaur remains that were found nearby.
Pazin in the heart of Istria is noted for its karst cave where the Pazin river plunges underground. The cave is said to have inspired Jules Verne for his fantastic stories. 
Take a peek into the shipwreck of the Baron Gautsch, an Austrian passenger ship which sank in 1914. It lies 40m below the surface 6 nm southwest of the island and lighthouse named Sveti Ivan na Pučini. The ship is a protected site so diving is only permitted through registered diving centres. It is incredibly well preserved, still displaying its belle époque beauty. And speaking of boats, visit the misleadingly-named Eko muzej Batana at Rovinj, which has nothing to do with organic vegetables but is all about a traditional type of boat, the batana.