Strength, utility and beauty
In the years when Augustus ruled Rome, the architect Vitruvius wrote ten books On Architecture, and in the first one he sets out a simple rule: every building should have strength, utility and beauty. The order of the three is worth noticing. A Roman building had to stand and had to work, and the Romans were happy to spend their best engineering on things a Greek architect would barely have called architecture, such as a water channel or a road.
That is the first difference from the Greek world. The Greek temple was built with posts and beams, what architects call trabeated construction (from the Latin trabs, beam): columns carry a horizontal stone, and the span is limited by how long a stone beam can be before it cracks. Rome kept the columns, the capitals and the pediments, but it also learned to build in a different way.
A new material and an old shape
The new material was concrete, opus caementicium: a mix of lime, volcanic ash and rubble that set into an artificial stone and could be shaped while it was still soft. Vitruvius noticed that the volcanic powder found around Baiae and Vesuvius, mixed with lime and rubble, hardened even under water. Walls could now be cast as one solid mass, faced with stone or brick, and curved forms became much easier to build.
The old shape was the arch. It was not a Roman invention, but Rome used it everywhere. An arch is made of wedge-shaped blocks that press against each other, so it can cross a wider opening than a beam and carry a heavier load, as long as its supports resist the sideways push. Extend an arch in depth and you get a vault; turn it around its centre and you get a dome. With these three forms, a building no longer needed a forest of columns to hold up its roof.
Why put columns on an arch?
Look at the Theatre of Marcellus, inaugurated in 13 or 11 BCE beside the Tiber. Its curved façade is a row of arches, one on top of another, and each pier between two arches carries a half-column pressed against it: Doric on the ground floor, Ionic above. The columns hold up nothing. The arches do the work, and the Greek orders stay on as a frame that gives the façade its rhythm and its dignity. This combination, the arch framed by columns, became one of the signatures of Roman building, and the Colosseum repeats it storey after storey.
Architecture from the inside
Concrete and vaulting let Roman builders think from the inside out. The Pantheon, rebuilt in its present form under Hadrian (118-125 CE), is a cylinder of brick-faced concrete with walls more than 6 metres thick, covered by a dome 43.30 metres across. The height from floor to top is the same as the diameter, so the whole room could hold a sphere. Outside, the building shows a conventional temple porch with Corinthian columns. Inside, there is a single space lit by one opening in the roof, and nothing like it had been built before.
Baths, basilicas and imperial halls followed the same logic. A Roman bath complex was a sequence of vaulted rooms, cold, warm and hot, with heating under the floors and water arriving from far away. The Greek world had admired buildings from outside; Rome built rooms meant to be experienced from within.
Roads, water and a city’s worth of building types
The second difference is scale. In 312 BCE the censor Appius Claudius began two works at once: the Via Appia, the first of the great Roman roads, and the Aqua Appia, the first aqueduct of Rome. By the end of the first century CE, nine aqueducts brought water into the city. Sextus Julius Frontinus, who was put in charge of them in 97 CE, compared these “indispensable structures” with “the idle Pyramids or the useless, though famous, works of the Greeks”. It is the most Roman sentence ever written about architecture.
Rome also multiplied building types, each with a job: the temple on its high podium, the basilica for law courts and business, the theatre and the amphitheatre for crowds, the baths, the market halls, the apartment blocks (insulae), the triumphal arch. Put together, they made up the Roman city, and the same set of buildings was repeated from Britain to Syria. That is why the plan of a Roman town matters as much as any single monument.
So what made it different?
Roman architecture kept the look of Greece and changed the way buildings stood up. Concrete and the arch freed the plan from the column, opened up large interiors and made it possible to build infrastructure on the scale of an empire. Many of these buildings still stand, and some are still in use: the Pantheon has been a church since 609, and one of the ancient aqueducts, the Aqua Virgo, still feeds the Trevi Fountain.
Where to see it
Rome has the best examples within walking distance of each other: the Pantheon, the Theatre of Marcellus, the Arch of Titus in the Roman Forum and the Arch of Constantine beside the Colosseum. Porta Maggiore and the arcades of the Parco degli Acquedotti show the aqueducts. For a route through the city, see the Rome guide for art lovers.
Sources
- Vitruvius, On Architecture 1.3.2 and 2.6.1 (trans. Gwilt, LacusCurtius).
- Frontinus, De aquis 1-16 (trans. Bennett, LacusCurtius).
- Ministero della Cultura, “Pantheon” (dates, dimensions, church since 609).
- Encyclopaedia Britannica, “Pantheon”; “Arch”; “Roman road system”.
- Turismo Roma (Roma Capitale), “Teatro di Marcello”; “Porta Maggiore e il Sepolcro di Eurisace”; “Fontana di Trevi”.
- Parco archeologico del Colosseo, “Arch of Constantine”.
- UNESCO World Heritage Centre, “Via Appia. Regina Viarum” (1708).
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