I am looking to book a tour to Italy next year. The itinerary marks some excursions as "when available" including St. Marks Square and Basilica, and the pantheon. These are obviously places that I would like to see, how do identify when these are not on the itinerary so that I do not book those dates?
It’s way too early to book those visits so I guess that’s what tour company means
Pantheon is free, only needs booked entry NOW on weekends
That will probably go away soon
Sometimes places are closed to the public on short notice for some official reason, and there is not much that a RS tour can do about it. While not likely, it's just a heads-up that things can happen.
More than once while on a tour, planned excursions have been moved around to accommodate unexpected closures. I'm sure they will do the best they can.
It also may mean when a guide is available. They likely use local people for those sites, they may or may not be available on the date you are there.
Both of course would be available to visit on your own, the Pantheon you can do yourself with a bit of research and available audio guides, similar with St. Marks square and the basilica, but obviously more there to see.
I agree that this means as long as the site is open to the public, they will go to the site. I do think you could look at the website for the Pantheon and see if they have any posted closing dates. The trick is, sometimes things change at the last minute.