We initially planned on taking a ferry from Venice to Rovinj but that shut down due to flooding (ferries run mostly in the summer, we were there late fall) so that’s the ideal route but there is also a train/bus option: take the train from Venice to Trieste, then take a bus from Trieste to Rovinj.
I very highly recommend Rovinj, its a small and beautiful town surrounded by Mediterranean ocean scenery. It was the highlight of E Europe for me. That national Park is also supposed to be AMAZING, my friend from Hungary goes there on vacation and take the prettiest pictures! From Rovinj,we went to Pula. Go to Pula!
There is a Roman arena there which is absolutely spectacular and, unlike most Roman ruins in Italy, must less overpopulated by tourists. Of course, we went in the off-season, but I kid you not, we were alone standing in the very middle of the whole arena. It was one of the most amazing moments of my life. Pula is a really neat city I think, the people are really fun in Croatia! Funny food and music and dancing- just smile & you’ll make 900 friends. We even accidentally attended a wedding one day!