How an arch stands up
An arch is a curve of wedge-shaped stones, the voussoirs, set side by side so that each one presses against its neighbours. The central one is the keystone. Load from above squeezes the wedges together instead of bending them, which is why an arch can span a wider opening than a flat stone beam, the lintel, and can be built from smaller blocks. The catch is that it also pushes outwards, so the piers on either side must be heavy enough to hold it, and while it is being built it needs a temporary wooden frame underneath until the keystone goes in. Picture two books leaning against each other on a shelf: they stand only as long as something stops their feet from sliding apart.
So who invented it?
Not the Etruscans. The barrel vault, which is simply a continuous series of arches deep enough to roof a space, appeared first in ancient Egypt and the Middle East. The old story that Rome learnt the arch from its Etruscan neighbours is therefore half true at best: the Etruscans used the stone arch, especially in the gates of their city walls and gates, and Rome grew up beside them. What Rome learnt from Etruria for certain is the temple. The most famous example is the temple on the Capitol, not a gate.
The gate of Perugia
Perugia, Etruscan Perusia, sits on a cluster of hills above the Tiber valley; it was one of the twelve strongholds of the Etruscan league and came under Rome in 310 BCE. Large stretches of its Etruscan walls survive, with three gateways. The walls date to the fourth century BCE, and the gates were opened in a major building project around the middle of the third century.
The Etruscan Arch was the only military entrance on the northern side. Two sturdy towers, trapezoidal in plan and narrowing as they rise, stand about 20 metres high on either side; between them the arched gateway, about 10 metres high, is built of large blocks of stone. Two granite blocks at the sides may have been human heads, perhaps protective gods watching the entrance.
Why it is also called the Arch of Augustus
After the Perusine War of 41-40 BCE, the future emperor Augustus reorganised the town, and its new name was carved across the arch: AUGUSTA PERUSIA. A second inscription higher up, COLONIA VIBIA, records the status of colony granted by the emperor Vibius Trebonianus Gallus (251-253 CE), who came from Perugia. In the Renaissance a loggia was built on top of the left tower; today it houses the regional office for archaeology, fine arts and landscape. One gate, in other words, carries three periods of history, one on top of the other.
Volterra and the other arched gates
Perugia is not alone. At Volterra, the Etruscan Velathri, the walls were enlarged in the fourth and third centuries BCE, and two Etruscan-Roman gateways survive. The better known, the Porta all’Arco, has three worn stone heads on its arch, read by some as Jupiter, Juno and Minerva, by others as the Dioscuri or as lions guarding the town. Its date is debated: some accounts place the whole gate in the fourth or third century BCE, others think the arch itself was rebuilt in the second. Either way, these gates belong to the last centuries of Etruscan Italy, when Rome already ruled or was about to rule the cities and the Roman arch was already on its way to bridges, aqueducts and amphitheatres.
Where to see it
The Etruscan Arch stands on the northern side of the historic centre of Perugia, in the line of the Etruscan walls. On the outskirts of the city, the Hypogeum of the Volumnii, an underground family tomb of the second century BCE, shows the Etruscan families who lived inside these walls. The Porta all’Arco still opens in the walls of Volterra.
Sources
- Umbria Tourism (Regione Umbria), “Etruscan arch of Perugia”.
- Encyclopaedia Britannica, “Perugia”, “Arch”, “Vault”, “Volterra”.
- Visit Tuscany, “Porta all’Arco, Volterra”.
