Favorite low key spots in Rome

In the afternoon I really enjoy sitting on the Piazza Rotunda (I sit on the far side of the Pantheon, right behind the fountain) and having a glass of wine with a light lunch. In the evening I head to Trastevere and hang out inside and outside of Santa Maria in Treastevere. Late at night (my favorite last thing before bed) is to have a gelato on the Piazza Navona. I sit on the steps of Sant' Agnese and just relax near the Four Rivers fountain. It just feels good to be there. Those really are places where I don't feel like a tourist, even after more than a decade! Sigh! I do love being in Rome!

Palazzo Barberini can be a nice, uncrowded visit. I personally want to get back to Trastevere and the new Testaccio food market on my next trip.

The Basilica of Saint Paul Outside the Walls is pretty cool.
https://en.wikipedia.org/wiki/Basilica_of_Saint_Paul_Outside_the_Walls

Have you taken the elevator to the top of the Victor Emmanuel Monument? The view from the top is spectacular!

If you have time, take a day trip to Tivoli. It's about an hour outside of Rome, and aside from the beautiful villas you can tour, there is great hiking and delicious restaurants!

I like bar della pace. I think it use to go by the name antica cafe della pace. Anyways it is about two blocks west of Piazza Navona.

Sit outside and relax.

Pack a lunch, find a bench in the Borghese Gardens and sit and people-watch.

I'm surprised that most responses only consider areas that are very much in the city center - therefore, not low key at all, given the amount of tourists around :)
As a local I'm always shocked at the amount of visitors who have never heard of Quartiere Coppedé, Garbatella or Monte Sacro. They're easily reachable by bus or subway from the hub at Termini and they all offer a glimpse of Roman architecture and history seldom covered by guides. It's places where I myself go for a walk, an authentic meal or just to sit on a bench and... be, when it all gets too overwhelming.
I highly recommend taking a stroll to just one of them, if you're on a tight schedule. Especially if you feel you have visited all the fundamentals already.

Palazzo Barberini is up a significant incline, perhaps take a taxi if you decide to go there.

You could take a bus to via Appia Antica and walk a bit there. Very low key. Stopping every half-mile to rest might pose a problem in some stretches, but it's not impossible.

San Giovanni in Laterano has plenty of resting areas, and it's close to San Clemente, a beautiful early Christian church built on several levels. Even if you can't descend to the lower levels, there is a beautiful mosaic on the ground level.

Near Santa Maria Maggiore is Santa Prassede (check opening hours), very beautiful and small enough to enjoy without crowds.

I would say the appia antica and Parco aqueducto. Quiet, normal life going on, and Roman ruins

The #118 bus, which goes down the Via Appia Antica, now departs from (and returns to) a stop labelled Ara Coeli/Piazza Venezia. This is located about 20 yards south of the Ara Coeli steps and Cordonata ramp. On weekdays, the bus goes down Via dei Fori Imperiali past the Colosseum and so on through the Porta San Sebastiano onto the Via Appia Antica. It passes the Domine Quo Vadis Church, the Catacombs of San Callisto and the Catacombs of San Sebastiano. After that, it turns left off the Via Appia Antica and goes further south, reaching the Villa dei Quintili. It then continues on south and returns back past the Villa dei Quintili, past the Catacombs of San Callisto and back to Ara Coeli.

On weekends, the Via dei Fori Imperiali is closed to traffic. So the #118 bus departs as before, circles Piazza Venezia and returns past the Teatro di Marcello and so on to the Via Appia Antica. In this route it does not go near the Colosseum.

To get back to Rome from the Catacombs of San Sebastiano you can either walk to the bus stop at the Catacombs of San Callisto or take the #118 bus south, knowing that it will eventually return to Rome. This return journey probably takes about 30 minutes longer than a direct bus journey but there is no bus going directly to Rome from the Catacombs of San Sebastiano.

There is small coffee/snack shop attached to the church at the Catacombs of San Sebastiano.

The Via Appia Antica is possibly narrow for walking on between Domine Quo Vadis and the Catacombs of San Sebastiano. There is a certain amount of traffic. There is a modern road inside the grounds of San Callisto (closed Wednesday?). Some of this is uphill.

The Villa dei Quintili dates to around 180 AD, the time of Emperor Commodus, who lived there. It consists of a one room museum and Roman ruins set in countryside. There is also a back entrance, not reachable by bus, adjoining the Via Appia Antica, which is open only on weekends. A journey by #118 bus from Ara Coeli to the Villa takes about 40 minutes. The return #118 bus stop is located across the motorway from the arrival stop. There are traffic lights for crossing.

The Villa ruins are a few hundred yards from the back of the museum building. There is a modern path up an incline to reach them. They consist of a Roman bath system and residential area. There are signs describing the different areas. Further on, beside the Via Appia Antica, there was originally a fountain. Over to the right (North) there is the medieval church of St. Maria Nova (not yet open/restored) and the back entrance/office (open weekends only).

There are some steps here and there as you walk around the ruins. The ruins are fairly complete. There is some plain marble mosaic flooring.

Bus information is available on maps at www.atac.roma.it

I'll put in another big vote for the top of the Victor Emmanuel Monument.
The elevator takes you to the top and you can see all over Rome, spend your time taking lots of photos and enjoying the views.

I like David and Ciaran's tips. We've been to Rome perhaps 0 times and I'll be sure to check out some of their suggestions next Sept. I would add a bus trip up to the Gianicolo Hill. You can also walk up (or walk down if you take the bus up). The view of the entire Eternal City and the Vatican is magnificent with the impressive statues of Garibaldi and his wife Anita who is holding a baby and a gun...cool stuff. It's a great place for a picnic.

Oops, meant to say 10 times in Rome.

We really enjoyed Appia Antica when we were there - it was a Sat I believe in mid-Sept - not many around - saw some wedding photos being done.

And last trip we visited Borghese Gardens and the Zoo. Again - a nice big park, so a good spot to relax - they have bike rentals and other rentals as well to get around the park.

Thank you all for your great ideas! Anyone know what type of weather we should expect in mid March?

I just returned from Italy with five nights in Rome a month ago. The Monti neighborhood (near Cavour metro), where I stayed, is definitely lower key--feels likes a real neighborhood. The Keats-Shelley House right off the Spanish Steps is a sight that really resonates with me, if you have an interest in English literature it's a real winner. Outside there are crowds on the Steps, but inside you have the place almost to yourself. They told me about the Non-Catholic cemetery, which houses the remains of Keats and Shelley. On my last day in Rome, before heading to Orvieto, I paid a visit. Incredibly peaceful site very near the Pyramide metro stop. The Borghese Gallery is a very easy visit, but you have to book ahead. Very limited entries allowed which makes it very civilized compared to Vatican Museums where part of the point seems to be putting you through a big hassle to remind you how popular they are. If you think you don't like sculpture, this place will make you reconsider. They are have some great paintings, including Girl with a Unicorn by Raphael (which was on tour in S.F a few year ago). I think the Castel S'Antangelo is very, very underrated too, and has a nice café with great views on the top level. With mobility issues, might have to rely on taxis more in Rome, but don't let that hold you back. Addendum--I went to the Victor Emmanuel Monument my first night in Rome, and thought it was pretty fun, certainly the views are spectacular. I found the crowds at the Capitoline Museums to be very manageable a few weeks ago despite it being the week leading up to All Saints Day.

I, too, enjoyed the Non-Catholic Cemetery, not least because it has cats. It's behind a wall, so check the website for opening hours before heading over.

The 2 famous hills, Gianicolo and Aventino are lovely park- like areas with gardens and gorgeous views overlooking Rome. Also Borghese gardens, huge area with terrific walking paths. All 3 places offer great respites from Rome's hustle/bustle.

I, too, enjoyed the Non-Catholic Cemetery, not least because it has cats.

It also has Gramsci's gravesite.

The Cemetery is one of my favorite places in Rome. Here is it's "proper" name, according to their website: Non-Catholic Cemetery for Foreigners in Testaccio, and many religions are represented-Orthodox Christians, Jews, Muslims and other non-Christians. Also buried there are the poets Shelley and Keats, among some other literary luminaries. Nearby is the Pyramid of Cestius. I remember as being easily accessible and I like to visit every time I find myself in Rome. I enjoy the free-roaming cats, too!

The Giardino Degli Aranci is one place in Rome I hope to get to on a future visit.
http://www.romeing.it/giardino-aranci-rome/

On the subject of weather, you can check on a website such as www.wunderground.com, a day or two before travelling, to see what conditions are like for up to ten days ahead. It should be accurate for seven days ahead.

I should have said on my previous posting, about the Appian Way, that San Sebastiano is closed Sundays, San Callisto is closed Wednesdays and Villa dei Quintili is closed Mondays.

I have found in Rome that rain can sometimes come suddenly and heavily after 4.00 PM on a perfect day.

My favorite low key spot in Rome is the Palazzo Doria Pamphilj http://www.doriapamphilj.it/roma/en/collezione-doria-pamphilj-catalogo-generale-dei-dipinti/j. It's a short walk from Santa Maria Sopra Minerva (another winner). It's a "one off" museum like the Wallace Collection in London; a great art collection in a beautiful building without the crowds of the blockbuster sights.

On our recent trip in September, we really enjoyed visiting Nero's Palace (Domus Aurea) near the Colosseum. You definitely need to make a reservation in advance (make sure you reserve a tour in English). It was really fascinating and hubby and I enjoyed it immensely! The sheer size and magnitude of the palace are incredible. Be sure to take a jacket with you as it's really chilly inside.

We also enjoyed a visit to Trajan's Market and as others have suggested, the views from the top of the Vittorio Emmanuel Monument are nice.