Outside the Porta Praetoria, at the end of the street leading out of the Roman city, stand two monuments a hundred and fifty metres apart. Neither costs anything, both can be seen at any hour, and both carry a history that runs well past the period they were built in.
The first is an honorary arch of 25 BC that in the Middle Ages was a house and then a fort, and that now wears a roof put there to keep it dry. The second is a perfectly preserved Roman bridge with no water under it, because the torrent it was meant to cross went away of its own accord.
An arch for a victory, and above all for a road
Why does Rome put up an honorary arch at the bottom of a mountain valley? The arch was raised in 25 BC to celebrate the Roman victory over the Salassi, won by Aulus Terentius Varro Murena, and it belongs to the same year as the founding of Augusta Praetoria. It has a single archway 11.40 metres high beneath the keystone, built of small conglomerate blocks.
Its position says more than its dedication. The arch stands on the axis of the maximus decumanus, just outside the walls, near the eastern entrance to the city and the district still called Bourg Saint-Ours. Anyone arriving from the plain met it before anything else, and passing beneath it entered, in effect, the territory of the colony. This is not a monument to a battle: it is a sign at the head of a road, and the road was the real reason Rome had fought the Salassi.
Today the arch sits in the middle of a roundabout, with traffic circling it. That is less solemn than you might wish, and at the same time it is the most faithful thing to its original spirit: it was built to stand on a busy road, and it still does.
Corinthian below, Doric above
Look at the arch for thirty seconds and you will see something odd. The ten half-columns decorating the fronts and the flanks end in Corinthian capitals, the ones with acanthus leaves. But the entablature running above them is of the Doric order, with its band of metopes and triglyphs.
In classical grammar the two orders do not mix like this: a Corinthian capital calls for a Corinthian entablature, with a continuous frieze. Here instead the designer took the richest element for the columns and the sternest for the band above. This is not a provincial’s mistake: Roman architects working at this scale knew perfectly well what they were doing, and various explanations have been put forward. What matters to you on the spot is knowing how to look: raise your eyes from the capital to the band above and the difference is visible without help.
Saint-Voût: when the arch was a house
Here is the part that makes this monument different from every other Roman arch in Italy. What happens to a triumphal arch when the empire that built it no longer exists? In the Middle Ages this one was not abandoned, not dismantled and not fenced off. It was lived in.
It took the name Saint-Voût, «Holy Face», from an image of the Saviour placed on it. In the 12th century a local noble family lived inside it, and in 1318 a small fortification for the corps of crossbowmen was built within it. A Roman honorary arch turned into a military post, with armed men inside and a saint on top.
That sequence, house and then fort, is not a picturesque anecdote: it is the reason the arch is still standing. In the medieval Aosta Valley a Roman building that served no purpose became a stone quarry. A building that served somebody was maintained. The same holds for the arch as for the eight towers of the Roman circuit that are now a conservatory, a school and an exhibition hall.
The roof of 1716, a restoration you cannot miss
The slate cap the arch wears on its head jars, and it jars on purpose. It is not Roman. The solution goes back to 1716, when the attic that once crowned the monument had gone and water was getting in and damaging it: the Aosta authorities decided to replace that attic with a slate covering.
It was a choice made three hundred years ago to criteria nobody would adopt today, and for that very reason it deserves respect. Whoever decided on it was not trying to make the arch look older: they were trying to keep it dry, using the materials of the valley, the same stone slabs that roof the houses and bell towers of Aosta. Warning: the roof you see today is not the one laid then. The monument’s present appearance comes from the last restoration and consolidation, of 1912, which included rebuilding the covering and was directed by Ernesto Schiaparelli, superintendent of antiquities for Piedmont, the Aosta Valley and Liguria from 1907 and also the man behind much of the collection of the Egyptian Museum in Turin.
The crucifix of 1449, and why what you see is a copy
A wooden crucifix hangs under the vault. Almost every visitor photographs it believing it ancient, and in a sense it is: its story begins in 1449. But the object you see is a copy.
The original was placed there as a votive offering against the flooding of the Buthier torrent, which runs a little to the east. In the 15th century the floods of that torrent were a serious problem, serious enough to make people hang a crucifix on a Roman monument in the hope that it would help. The original is kept today in the Treasure Museum of the cathedral, which I write about in Aosta cathedral, the mosaics and the treasure.
Keep that in mind, because two paragraphs from now it turns into an unintended joke by history.
The stone bridge, and the river that walked away
A hundred and fifty metres east of the arch stands the stone bridge, in French pont de pierre, built when the city was founded to carry the road from one bank of the Buthier to the other.
You arrive, you look, and for a few seconds you cannot tell what is wrong. Then it lands: under the bridge there is grass. Not a bed that dries out in summer, not a trickle: grass, trees and a path.
In the Middle Ages an exceptional flood made the Buthier change course and move its bed westwards. A modest channel went on running under the arches and in time dried up altogether. The result is an intact Roman bridge that no longer crosses anything.
Now put the two things together. The Valdostans of 1449 feared that torrent enough to hang a crucifix on the arch of Augustus to keep it friendly. Some centuries earlier or later, the torrent had already decided on its own to go elsewhere, leaving high and dry the bridge that had been built expressly for it.
Why that bridge is so low and flattened
Why did the Romans, who loved the semicircular arch, squash this one? The bridge has a single segmental arch, rests on footings of puddinga, the local conglomerate quarried along the Dora Baltea, and measures about seventeen metres between the two springings. The passage is about six metres wide, parapets included.
The thing to notice is the profile. The vault, built of large voussoirs, has a rather flat outline for Roman construction, with a span-to-rise ratio of three to one. As a rule the Romans preferred the semicircular arch, which is simpler to build and carries loads better; a segmental arch is what you use when the road must not climb and drop again, when what matters is ease of passage rather than purity of form.
Which is exactly the case. At Aosta the transalpine road towards Gaul, the via delle Gallie, branched for the Little and the Great St Bernard; heading for the Po plain it left the valley over another segmental-arch bridge, the pont Saint-Martin, which is beautifully preserved. This bridge was not urban ornament: it was a piece of the imperial road network, and it had to carry carts.
Practical information
Details checked on 7 September 2026. These being open-air monuments, there are no prices to check again here: what changes is the traffic around them, because of the building work under way in the city.
Tickets. Nothing to pay. The arch of Augustus and the stone bridge are open-air monuments, freely accessible, and they are not part of the «Aosta Archeologica» ticket, which covers the five indoor sites.
Opening times. They can be seen at any hour of any day, holidays included. The arch is floodlit at night, and it is one of the few cases where a night photograph works better than a daytime one, because the raking light lifts the half-columns off the background.
Getting there. The arch stands at the eastern end of via Sant’Anselmo, the street continuing beyond the Porta Praetoria: ten minutes on foot from the centre, a quarter of an hour from the railway station. The bridge is a hundred and fifty metres further east, reached by carrying on in the same direction, and you can go down to the level of the grass from the side garden.
How long it takes. Twenty minutes for both, half an hour if you walk round the arch to see the entablature from both sides. This is the right stroll for sunset, when the ticketed sites have already shut.
Warning: the arch stands in the middle of a busy roundabout, and photographing it properly means crossing. The best spot is the lawn to the west, where the benches and the hedge are.
The rest of Aosta
Arch and bridge keep no hours, so they slot in wherever you like on a day that keeps a great many: that whole day is in what to see in Aosta in one day. The other pieces in the cluster are the Roman theatre and the walls of Augusta Praetoria, the collegiate church of Sant’Orso with the cloister and the forty capitals, the cathedral with the choir mosaics and the treasure museum and the megalithic area of Saint-Martin-de-Corléans.
If this pair has caught your interest, the closest comparison is Rimini, which has the other great Augustan arch, of 27 BC, and the bridge of Tiberius, the other Roman bridge that lost its river when the Marecchia was diverted. A third reused Roman arch, moved twenty-eight metres and saved by Victor Hugo, stands at Saintes, in France.
Photo credits: arch of Augustus by Krzysztof Golik (CC BY-SA 4.0), arch from the side by Tiia Monto and stone bridge by Tenam2 (CC BY-SA 3.0). All from Wikimedia Commons.
