How to fill an open day in Rome after everything else has been seen

Lots of great 'worthwhile' things to see in Rome BUT you have to give us some sort of idea what trips your trigger. I can send you to some great stuff that appeals to ME but without knowing what you've already booked, it doesn't help.

So give me an idea of what you've booked, and what kind of things you're interested in?

Have you considered the Baths of Caracalla? We found them to be a peaceful, fascinating place after the crowds of the Vatican, Colosseum etc. They are close to the Colosseum.

Ostia Antica, Hadrian's Villa/Tivoli, or Orvieto are some nearby day trips. Pompeii is doable but very long. Within Rome, you can check out the Appian Way. IIRC, it's closed to cars on Sundays. You can also go to the Aqueduct Park and rent a bike or walk around. If you haven't visited one yet, a tour of the catacombs is a good option. Pretty much every church is like a museum so you can walk around a pop in to every church you see.

Again, kraczz, we can throw out suggestions all day long but we don't know what might appeal to you, or if you are traveling with children, by yourself, with someone who might have difficulties getting around on foot, etc. The more you can tell us about yourself/your traveling companions, the better we can help you.

Check out Basilica San Clemente, near the Laterano stop on Line A. Fantastic mosaic, interesting frescoes, but mostly for the amazing excavation under the basilica. Travel through two thousand years of Roman history. Good gelato nearby.

San Clemente and Orvieto.

The Baths of Caracalla are wonderful. Also the St Peter's in Chains church - one of my top Michelangelo statues is there - Moses. Ostia Antica. Orvieto isn't always doable... depends if they finished the work that was going on earlier this year but normally it is a good day trip. Orte is a easy train ride away and the upper town is great.

3 days?!
You must be joking.

True...Davebarnes is right. I've been in Rome a total of a month over 3 trips, and truthfully I haven't scratched the surface...

Honest, my absolute favorite thing to do in Rome is to be there for a few days at an AirBnB in a cool neighborhood, and just 'be'. Get up in the morning, go for a walk, shop for breakfast at a market...fruit & pastry...come back to the apartment, linger over some coffee and decide what to do that day. Something, or nothing. There are far worse things than sitting at an outdoor cafe for a couple of hours, nursing a Aperol spritz and people-watching.

Hope you get an opportunity to do that--maybe next trip to Roma.

Been there, done that, bought the t-shirt :)

You specifically said day trips. Some easy, common, and cool ones are: Ostia Antica, Orvieto, the Appian Way. I think Naples is a great day trip, but Pompeii is a bridge too far (though people do it apparently.)

BUT, I think the forum’s subconscious is pointing towards a deeper Rome cut. In that vein, I agree that some “downtime” in Rome is essential to appreciating the city. Explore Trastavere or Testaccio for a taste of neighborhood Rome. Pop into the small churches and squares. Eat all the street food. One of my favorite memories was just wandering through central Rome, finding myself in some rather magnificent churches that didn’t make the guidebooks.

I was being rather supercilious with my last comment, but yes, you are correct, the OP was asking for day trip suggestions.

It was the "seen everything" in the title that threw me. I'm sure the OP doesn't actually mean that they have seen everything. That would be daft in a major city like Rome. Even ticking off tourist sites like rides at Disney would take longer than three days in Rome surely?

Whether you take a day trip or not OP, a day doing nothing but hanging out, drinking coffee and taking in the atmosphere is not a day wasted. That's what cities are good for.

Return to that place you passed, but wasn't on your schedule before. Walk through the gardens and neighborhoods of Rome and soak it all in since you didn't have time earlier. Go on a gelato hunt. Have a leisurely lunch on the sidewalk of that restaurant you walked by where everyone was having a good time and the food looked delicious.

No reason to go on a day trip. You have much more of Rome to discover.