Recommendation on Castel Sant'Angelo?

I have never than a Rick Steves Tour.
I have visited Castel Sant'Angelo (Hadrian's Mausoleum). I think we spent about 3/4 of an hour there at the most.
It was interesting, but not a top tier site to see in Rome.

I thought the Castel was fascinating. There was so much history and so much to see. Everywhere you went there was something new waiting for you around the next corner. You can also have a light lunch/drinks at the top with an incredible view of the city. That was the case prior to Covid. I can't wait to go again and spend more time there.

I also went to Castel Sant'Angelo last time I was in Rome, and absolutely loved it. It has some great history, quite a few things to see, and some great views from the top and the various vantage points. And, after dealing with massive crowds, it was nice to do some sightseeing with plenty of elbow room.

Use your time to visit the important sites in Rome that the tour doesn’t visit. I am surprised how little is covered in Rome by this tour.
I have been to Rome four times but have never gone to see Castel San Angelo.
What about visiting one of Rome’s real gems the Pantheon?? Next, walk to Palazzo Navona nearby. Cross the Tiber River to walk around the neighborhood of Travestere.
Pompeii as a day trip from Rome is too far. Save it for a trip to Naples, Sorrento or the Amalfi Coast.
Ostia Antica is an easy day trip from Rome.

I kind of agree with Suki's comment above, but if you have done the standard high street walks like the Ramblas and the Champs Elysee etc etc then it is interesting to compare the Via della Conciliazione walk between Piazza San Pietro and the Castel Sant'Angelo -- esp. if you do your research ahead and learn about the fascinating buildings (stores, embassies, libraries, palaces) along the way.

Are you seeing the Borghese as part of your tour? If not I would try to get tickets there. We are headed to Rome for our 4th time (other times were on RS tours) and I have Castel Sant’Angelo on the list to see. Been past it so many times really want to see it. The Palazzo Massimo is amazing. Near the Termini station. Not crowded. I would suggest there also we went there before our RS Rome tour.
Enjoy

If you are coming from the States, it's nice to spend the first couple of days getting acclimated before hitting the road. I'd avoid Pompeii because it would be a loooooong day unless you flew into Naples first and/or had a tour/driver organized. Our preferred way to get over jet lag is to walk, walk, walk. I'd look for experiences that aren't as nice with a group. The market at Campo de' Fiori is fun and open every morning. You can pick up some items that you might want for your trip like a linen shirt, hats, a salami or fruit. We went to Castel Sant' Angelo in May and liked it. Nice views from the top and not terribly crowded but not close to other things.. Are you going to the Capitoline Museum? I'd also find a nice place to have an aperitivo every day. It is a civilized way to have an afternoon break, get a nibble and people watch. They vary in quality but are generally around the same price. We went to one by the Pantheon that had an assortment including a caviar-ish substance on toast not just crisps and peanuts. I'd pop into any church you see as even the tiniest can be wonderful. That will give you a frame of reference for the big churches you visit later. We light candles in every one we visit. There are places you can enjoy an opera sampler program for a couple of hours in the evening. Cheap and doable. We really enjoyed the Twilight Trastevere food tour. We're not fond of tours but we would definitely do it again. It goes late and you walk a lot. Perhaps not best for your first night. However, it was interesting, tasty and a lot of fun. We were drawn back to some places for a second visit like Trevi Fountain after dark. How can you go wrong in Rome?

You'll have quite a bit of bus time on this excellent taste of Europe so I would not do Pompeii.

I've not been to Castel Sant'Angelo nor the Borghese but I'll be there in a few weeks and have a timed entry to the Borghese as well as the Domus Aurea. The Domus Aurea (Nero's palace) is only open on the weekends so it will depend on the days of the week that you are there for this one if it's of interest. Otherwise, I'm returning to the Capitoline Museum which I've been to before but is so excellent I'm going back. I'll try to get to the Baths of Caracalla this time.

For those replying that have not looked at the itinerary, the tour covers Saint Peter's, Colosseum, Forum and the Vatican Museum. It has a walk on the first night that will go to the Pantheon if available.

If you are out just walking around one of the places I went the first time I visited Rome was on a quick sightseeing car tour on the way in from the airport. He took us to the Aventine Keyhole through which you have a cool view of Saint Peters.

https://www.atlasobscura.com/places/the-aventine-keyhole-rome-rome-italy

We visited Castel Sant’Angelo on our last trip. It was our fourth trip, so we’d seen most of the other top sites, and we passed by it several times walking between our hotel and the historic core. It was a surprising hit, mostly because it wasn’t crowded it’s easy to navigate and had our favorite roof top view in Rome. I know it’s personal preference, but we liked the view from the Castel more than the view from the top of Victor Emmanuel.

As to other sites to see, I would definitely try to get tickets to both the Borghese Gallery and Domus Aurea. Our frequent travel style is to find out about things in hindsight and I’m glad we got to see both of those. I would also recommend the Capatoline, especially if you got to Domus Aurea, as they go together nicely. Ostia Anitca would be a good addition, but there are still some other great things to see in Rome, such as the Doria Pamphilj Gallery. It’s close to the Victor Emmanuel. I would also agree that visiting Trastevere is a fun experience, especially in the evening.

Maybe it depends on how much time you have and your preference for tours. We found Castel purely by mistake after a Vatican tour ended. We absolutely loved it and have been three times now and I would go again. We just think it's fascinating. The views as you get up are wonderful, especially at the top and there is a little cafe where you can order a glass of wine and sit and look out the carved out areas and see Rome around you. Again, maybe a personal preference but we never get tired of this location.

THANKS To All👍
I'm really into angels and love all of them, that’s why I was intrigued about this site. One of my favorites is a really funky one from Assisi - they are my favorite / and the only collectible anywhere in our travels. I think I must have 20 really unique and great memories from each place they are from, I play with photos also. So I’m hoping we make it there❣️Thanks for supporting the time to do this stop.