Venice to Barcelona cruise

Google for Tom’s Port Guides tomsportguides.com.
He’s put together free guidebooks for the ports you’ve mentioned. He has 46 pages with maps and photos on Montenegro alone. Bon voyage.

Have you visited the website: cruisecritic.com ? Its a bit difficult to navigate, but you can find some info on ports, excursions etc., including reviews and reports from individuals, as well as asking questions.

Well, your. cruise line will have excursions for sale, so look at those first. Cruise Critic will have advice for you, as someone has suggested. For Valletta, I suggest just going on your own. It is a compact city but do some research first on the many interesting things to see. (Google”Things to do or see in Valletta”). Do the same for the other ports. If you’re interested in Mt Etna I expect your ship will offer an excursion from Taormina. I would encourage you to take part in it.

Again, go to Cruise Critic for endless answers to millions of questions.

Just a "heads up". From Kotor there is a road that leads away from the bay inland. The views are spectacular. Absolutely beautiful. But, It goes up the side of a steep mountain that has 25 numbered 180 degree switchback turns and at least 75 other sharp turns. Rock wall on one side and nothing on the other. Can't remember the name or number of the road, but it went to the towns of Njegusi and Cetinje. Don't mean to rain on you parade, but don't want you to get into a hairy situation without any prior knowledge. If anyone in your party is prone to motion sickness or has a problem with heights you might want to avoid this road. You can go to bing.com, use the map feature, and see aerial views of the road from &*$$. You can also check it out on googlemaps.com. It is possible, however, to do other things around Kotor with using that particular road.

On 12 Mar. 2017 there was a thread titled "Greece Montenegro Croatia". One person included a link to the map that shows the road. Another person had a link to a video made along parts of the road.

As said above, Cruise Critic is hard to navigate. Here are some pointers.

Here's a link to their Oceania Roll Calls. Here you can find your specific sailing and meet others who will be on it. This is especially useful if you want to join others on a private tour, cutting the cost while still having fewer people and more customization than the ship's tours: https://boards.cruisecritic.com/forumdisplay.php?f=420

Here is their European Ports group listing. You'll see there are separate Forums for Italy, Spain, France, Greece, and other Mediterranean ports (Kotor and Valletta are in this last forum): https://boards.cruisecritic.com/forumdisplay.php?f=19

And here is their Oceania forum: https://boards.cruisecritic.com/forumdisplay.php?f=51

Cruise critic will have some information on each port. The people on the sight tend to be oriented toward ship's excursions. I like to do things on my own (or at least hire a local guide at 1/3 the price). I review cruise critic, however, to see what some of the options are at ports of call and what people thought of those choices. Your ship's website should also list the excursions they are selling in the different ports. If you like the destination, you can always do it yourself (faster and cheaper) than going with the big bus tours from the ship.

Thank you, everyone, for your advice. Yes, I have been on cruise critic and the Oceania website. I was just looking for anything additional. I am definitely not interested in the shore excursions Oceania offers. I would prefer a smaller group, more timely and less expensive. I know on the Roll Call others cruising organize their own small group excursions, and we are doing a couple of those. Many thanks to all of you~

Since you had been on several cruises, I assumed you were familiar with CC. I hope you find Tom’s information useful.

Yes, Bets - Tom's cruise guides for the ports are tremendously helpful and I thank you for that info!