Secreted away in an unassuming 16th-century church in Rome you’ll find traces of the once mighty empire — and the ruin and rebirth that followed its fall. Colossal ancient ruins, Renaissance astronomy and sheer architectural splendour await at the Basilica di Santa Maria degli Angeli e dei Martiri (Saint Mary of the Angels and Martyrs).
This is a place that’s seen it all. From the largest baths in ancient Rome, to a quarry and medieval hunting ground, to an opulent 16th-century basilica: Santa Maria degli Angeli e dei Martiri and its surrounds is imprinted with the story of Rome’s changing fortunes over the centuries.
The Basilica is located just a five-minute walk from Rome’s main train station, Termini, in a part of the city that some euphemistically describe as ‘colourful’ (read: sorta dodgy).
From the outside the Basilica looks rough, unfinished and, apart from the tell-tale cross, distinctively un-church-like. Its front façade is a concave, semi-crumbled brick wall, complete with tufts of shrubs spurting from the edges. All up, a far cry from the architectural grandeur and extravagance of your average Roman basilica.

Don’t be fooled by the underwhelming main entrance of the Basilica of Saint Mary of the Angels and Martyrs.
But don’t let this humble exterior fool you. What the Basilica lacks in gravitas externally it makes up for in interior opulence. Plus there’s a very good reason why, from the outside, the church kind of pretty much looks like a ruin — it kind of pretty much is.
This Basilica was built within the fabric of the surviving ruins of what was once the largest, most sumptuous bath complex in ancient Rome, if not the entire empire.
Ruins, re-use and recycling
The Baths of Diocletian were built here from 298 to 306 AD. The name is sort of a misnomer: though dedicated to Emperor Diocletian, they were in fact commissioned by his co-ruler Maximian. Reportedly nearly 11 acres in size, and able to accommodate 3,000 people, these Baths were larger than the Baths of Caracalla which are still around today.* Public baths such as these tended to be open to both rich and poor; even women and maybe even slaves could bathe here, though typically at different hours.
Hygiene and grooming were not the only reason that ancient Romans frequented public baths. They were also places to socialise, swim, relax, read and enjoy a massage or health treatment. The Baths of Diocletian also boasted Greek and Latin libraries and even theatre-style seating from which bathers could watch athletes competing. The Baths were basically an all-purpose leisure, relaxation and ‘wellness’ centre, something akin to a modern-day destination spa. One that, ancient Rome being ancient Rome, just happened to be built and powered by slaves.
But after the siege of Rome in 537, when the Goths cut the city’s water supply, the Baths gradually fell into abandonment and disrepair. Rich in marbles and rare stone, the once-opulent Baths of Diocletian then came to be used as an unofficial quarry, possibly for centuries.
This wasn’t unusual. Throughout the city, the materials of ancient monuments and structures were commonly pilfered and ‘recycled’ for use in buildings under construction. This practice was known as spolia (Latin for ‘spoils’). It’s likely many Roman churches and palazzi owe some of their fabric and embellishments — a column here, some mosaics there — to these plunders. So, why the rampant ransacking?
I mean, free construction materials for one thing, right? Plus… Thing is, it wasn’t only the Baths that had fallen into disuse. After the collapse of Rome, the city had lost not only its former glory as the epicentre of the western world but even its dimmed prestige as the western capital of the empire — and, later, home to the Papacy. And so its urban fabric fell victim to architectural pillage, dilapidation and decay.**
So ruined and overgrown were the Baths by the medieval era, in fact, that Roman noblemen were recorded using the site as a hunting and riding ground. Nature had by then reclaimed these ruins, on the outskirts of a city that was a mere shadow of its former marble-monumented self. A bizarre thought to entertain today when taking in the sirens, car-beeps, and traffic roar outside the Basilica. Or its splendour inside, for that matter.

Pieter van Bloemen (1674-1720), Landscape with Herdsmen and Animals in front of the Baths of Diocletian, Rome.
Nameless slaves, seven angels and a fanatic monk
The Basilica as it stands today all started with the vision / visions of a Sicilian monk called Antonio Lo Duca. He visited the Baths’ remains in 1541. After visiting checking out the site where the Baths stood in ruins, the story goes, Lo Duca had a vision. In his words (my translation, and my punctuation underlined***):
…fixed like a column, here, it seemed to be inside the Baths of Diocletian — inside the courtyard in front of the door of the Baths — a light whiter than snow, that went up, coming from the earth of the Baths, brighter than a crystal. In the first part it showed me more clearly inside the front [of] the said Baths …. as if I had seen with my own eyes…
A sequence of images then followed, Lo Duca reported, which he took as a sign that a church should be built right here, incorporating the Baths’ ruins, and dedicated to ‘the angels’. It just so happened, coincidentally I’m sure, that he had been fixated with this particular cult of the ‘Seven Angelic Princes’ since at least the 1510s, and had even travelled to Rome to beseech the pope for their veneration.
This vision of the bright light at the old Roman baths fired Lo Duca up even more. He set about lobbying the pope for a church to be built here in this spot and seems to have started a one-man letter-writing campaign asking wealthy would-be patrons to join him in his cause.****
Apparently somewhere along the way Lo Duca spared some thought for the Christian slave labourers who had, in ancient times, been forced to build the expansive baths complex to begin with. Hence both the ‘martyrs’ and the angels in the Basilica’s name. Mission success, in other words.
Certainly thousands of slaves toiled here during and after the Baths’ construction. While the free bathed, frolicked and pampered themselves, slaves maintained the complex from their underground passages — or, maybe even less pleasantly, scrubbed their masters with hot oil.***** But it’s impossible to say how many of them were Christian, and how much of the martyr story is legend rather than historical fact.
A masterpiece of a late Renaissance genius
At any rate, the next person to leave a mark on the site was no stranger to the historical record. It was to be the last church project of Michelangelo himself, then 86 years of age.
Construction on the Basilica began in 1563 to his design.****** But when Michelangelo died a year later, the project was passed on to his student Jacopo Lo Duca (nephew of Antonio — small world, right?).
The most striking thing about the Basilica is the way it is not only set on the imperial Baths’ ruins but incorporates them into its fabric. This gives you a real sense of the sheer scale of the Baths of Diocletian in their ancient heyday.

Ancient Roman walls of the former Baths of Diocletian. Image courtesy Giovanni Dall’Orto.
The underwhelming main entrance, for starters, marks the former caldarium (or hot bath) of the complex. It’s just one of the ways in which the original design played with space, structure and void with, well, exactly the kind of genius you’d expect from Michelangelo himself.******* As Andre Stiles noted in his thesis on the Basilica:
… [H]aving the patrons walk through the massive ruined hole in the facade creates, for them, a closer connection to the ruin. They literally reuse this portion of the building by entering through it and experiencing its decay.
Some aspects live on more strongly than others, however. Take the original vaults from the Baths of Diocletian, today serving as the nave of the Basilica — a slice of imperial Rome tucked into the ceiling of a 16th-century church.
Michelangelo’s design was attuned to the evocative power of the ancient ruins, and the site’s dual meaning as a Christian relic (legendary or not) of the forced labour of slaves. All brought together in a quietly spectacular place of worship amidst the Renaissance ‘rebirth’ of Rome. A phoenix of sorts.

The interior of the Basilica of Saint Mary of the Angels and Martyrs. Image courtesy Giovanni Dall’Orto.
And these aren’t the only ideological tensions etched onto the proverbial brick and mortar of the Basilica during its 450-year history.
A cosmic line between science and faith
Large, airy and vividly frescoed, the Basilica’s interior also features an unexpected curiosity engraved on its floor: a meridian line sundial, crafted of bronze and white marble. One of several in Catholic churches around Italy and beyond,******** the meridian line marks a curious interplay between Catholicism and astronomical science.
Curious and slightly eyebrow-raising, in fact, for anyone with even a cursory knowledge of Galileo Galilei’s persecution by said Catholic church just 70-odd years earlier…

Functional and symbolic: the meridian line of the Basilica of Saint Mary of the Angels and Martyrs. Image courtesy Jean-Pol Grandmont.
Typically housed in grand basilicas and cathedrals, meridian lines were a bit of a flex. They were meant to showcase the Church’s success in using astronomy to reform the Gregorian calendar and fix the date of Easter. Which flaunted, by extension, the supremacy of the Church over the pagan calendar of old. Yes. Weird flex indeed. If it all sounds a little abstract, architectural writer Geoff Manaugh explains the mechanics of how it worked:
As the sun tracks from north to south on its annual migration between the summer and winter solstices, its image on the cathedral floor also shifts, moving slowly along the meridian line. Halfway between the solstices, of course, are the spring and autumn equinoxes. Once the position of the solar circle indicates the spring equinox, believers must simply wait for the next full moon; the first Sunday after that full moon will be the proper date of Easter.
Indeed, one of the reasons this particular basilica was chosen out of Rome’s 900-plus churches as the best spot for the meridian line was its location on the site of the ancient Roman baths — once, famously, a monumental imperial project named for a pagan emperor. Here was a particularly resonant site in which to symbolically proclaim the superiority of the new Gregorian calendar to outdated pagan time-keeping. This exercise in self-congratulatory astronomical sass was completed in 1702.
In today’s digital world, where even many a wristwatch has been relieved of its time-telling duties by smartphone screens, these meridian lines are more tourist curiosities than useful astronomical tools. But this one remains in working order. Each day a ray of light seeps through a sneaky hole in the Basilica’s wall. If you ever find yourself in Termini with an hour to kill between trains, why not drop by and see if you can spot it?
Yeah, it might not look like much from the outside but the Santa Maria degli Angeli e dei Martiri is an architectural masterwork. It stands in testament to Michelangelo’s knack for adaptive re-use (or a precursor of it) centuries before the term was coined. The combined handiwork of a master sculptor, and untold thousands of nameless ancient slaves, working centuries apart — united by the vision of a Sicilian monk who just would not take no for an answer.
Because sheer architectural impressiveness aside, perhaps the most fascinating pieces of the Basilica’s story are, after all, a hole in its wall, a line engraved on its floor, and the traces of ancient ruins that still linger in its fabric.
*No mean feat, as anyone who has been there can assure you.
**It’s funny, we all hear about the rise and ‘conquests’ of the Roman empire but basically SFA about its fall.
***Because damn did medieval folk like those run-on sentences.
****Hence his letter above, written to a Signora Lucrezia della Rovere-Colonna, which fortunately survived out of who knows how many.
*****One slave’s name was actually recorded here at the Baths of Diocletian on a funeral stele/slab which reads:
Eros, Posidippus’ cook, slave, lies here.
Mmm. Real deep and meaningful, there, Posidippus. This blog from the University of Kent points out that as impersonal as the inscription may be, it did ensure the name of this dead slave lived on (presumably a few more millennia than intended):
Eros died a slave. His [sic] is only known by his first name – a name commonly given to slaves. His identity comes from having been owned by Posidippus and from his occupation. This inscription however, meant that he would not be forgotten by those who had known him.
******Just to put his output into perspective, this was some 55 years after he did the famous Sistine Chapel ceiling.
*******Four for you, Michelangelo, you go, Michelangelo.
********Bologna’s one is particularly famous. Personally I was more enamoured with the underground ruins beneath the library nearby.
Tips, Links and Resources
Visiting Basilica di Santa Maria degli Angeli e dei Martiri
What you should know before you go to the Basilica of Saint Mary of the Angels and Martyrs, Rome:
- Some handy visitor information at the bottom of this post from Rome.net.
- Price: free, but you may like to make a small donation.
- Tip: an interesting museum on Roman history — and one of the four parts of the Museo Nazionale Romano — is a close neighbour of the Basilica, set in the Palazzo Massimo alle Terme. It contains some fantastic Roman frescoes. Visitor info at the bottom of this post from Rome.net.
- Tip: if you’ve got a layover between trains at Roma Termini station and you’d like to check out some off-the-beaten-track destinations well within walking distance in the meantime, the Basilica of Saint Mary of the Angels and Martyrs and the museum next door are great options. They’re both about a five-minute walk. If you have a long layover or are travelling along you might like to check your luggage into the station’s left luggage facilities (look out for deposito bagagli) beforehand.
- Tip: another fascinating, lesser-known Roman church with a rich, ancient history is the Basilica of Santa Maria in Aracoeli. You can read my post about that here.
Learning More
Deep dive into the history of the Basilica with my super nerdy round-up of resources for learning more:
- An interesting thesis on Michelangelo’s re-use of ruins in this basilica, by Andre James Stiles.
- The Churches of Rome Wiki entry on the Basilica is worth a read for my fellow history geeks.
- The Sacred Destinations entry is also informative.
- Naples: Life, Death and Miracles has an interesting article on the rebirth of Rome in the Renaissance era
- A fascinating Atlas Obscura article on the role of meridian lines in churches (and why it’s more complex than you might think) –
- Learn more about Roman baths from the Ancient History Encyclopedia.