Italica was on the top of my list for Spain mainly because of the filming location used as the Season 7 finale of Game of Thrones. A great location indeed. It doesn't quite compare to big sites like the nearby Sevilla but it's a classic "ruin" that perfectly fits to world heritage.
Entrance was free even for non-Europeans at the time, the website states €1.50 which isn't a lot for the massive amount you get to see. The entrance to the site was also on the other side of the area which was temporary due the film crew (read: set construction) using the main access instead. Everyone was greeted and as soon as they figured I'm not Spanish I was just shuffled along inside, the rest was offered a guided tour (I assume not for free).
It is one of the biggest sites of Roman ruins although it is very ruined. A lot of of the main paths go along very short walls and column pieces - not very impressive by itself but after it took me 20 minutes to walk around I figured this place is REALLY huge. The amphitheater is the biggest draw and the location of the GoT scenes. Not only that but it could house 25,000 people, that's a lot and maybe the entire town! Due to the upcoming filming the site was partially blocked off and it was not possible to walk inside at that moment, as the site is to make a return in the eight season of the show. The second biggest draw are the mosaic floors - beautiful. Third, the thermal baths. Well I didn't find them as impressive as Rome or even the Turkish ones that are now lying in ruins, but which Roman city didn't need a thermal bath right. You can only see the outlines now so it's a little lacking a bit of uniqueness, not that anyone would come here to see just the baths.