If you get the chance to visit the Northen most part of Adriatic there is lots of interesting things to see. It’s better to visit it in low season when it is not so hot, because the water is not exactly clean to jump into, though it depends where you are.
We went for a short ride with a boat from marina Nautec in Monfalcone to Duino Castle and back. To visit the Castle you have to call ahead, and in winter time it is only open during weekends ‘till 4pm. During summer it’s open every day ‘till 4pm, except Tuesdays.
Under the castle there is a nice beach with a fabulous cliff above it and the water was clean enough to jump into it, only there were lots of very large jelly fish floating around…