Augusta Praetoria, the Roman Aosta

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Augusta Praetoria Salassorum was the name of the colony that Emperor Augustus had placed to guard the Alpine transit routes, and which we know today as the Roman Aosta. There, in fact, the consular road from Milan (Mediolanum) to Gaul ran along two main road axes: one towards Lyons (Lugdunum) by way of the Little St. Bernard Pass, while the other went over the Great St. Bernard and ended at Martigny (Octodurus).

The toponym of the Roman settlement reveals a multiplicity of historical meanings. Aosta was primarily Augusta, since it was founded by the emperor in 25 B.C.; Praetoria as it was settled there by some three thousand Praetorians; and finally Salassorum because the Celtic tribe of the Salassi stayed in these lands, inhabited from prehistoric times near the area of Saint-Martin-de-Corléans, since the second century B.C. Rome had attempted to civilize these peoples on several occasions: in 143 B.C. the consul Appius Claudius Pulcher had achieved a first major victory, however, it was only in 25 B.C. that Varro’s legions finally subdued them. Therefore, one can understand what the importance of Augusta Praetoria was for the strategic and military control of the region.

The Arch of Augustus in Roman Aosta

Visitors get to Augusta Praetoria by the Via delle Gallie, through the Arch of Augustus. The monument was erected in honor of the colony’s founder, Augustus, and was intended to make manifest the power of Rome to the subdued tribes. The arch, with a single barrel-vault and massive pillars of conglomerate blocks, is decorated with ten half-columns with Attic bases and Corinthian capitals. Of the original reliefs the Doric entablature with triglyphs and metopes remains, while the attic was removed in the 18th century.

Roman Aosta
The Arch of Augustus

The urban structure of Roman Aosta

Augusta Praetoria was built according to the typical Roman city planning. The settlement developed by means of a characteristic rectangle whose extension depended on the slope of the valley floor surrounded by mountains. Moreover, it had as its natural edges the course of the Buthier River to the east and that of the Dora Baltea River to the south. Aosta was entered through the gates located at the ends of the decumanus maximus, which represented the continuation of the Via delle Gallie: Porta Praetoria and Porta Decumana.

The main cardo intersected the decumanus at right angles and intercepted the city’s forum area, having the Porta Principalis Sinistra and Porta Principalis Dextera as its entrances. The urban structure was surrounded by the city wall, which still preserves its layout almost intact, made of opus caementicium with river pebbles and mortar.

Roman Aosta
Portions of the Roman walls of Aosta

Porta Praetoria

Porta Praetoria, the main entrance to the city, is built of stone blocks and slate formerly quarried from the riverbed; only a few portions remain of the original gray-green and white marble facing. It is articulated on two opposing series of arches, each provided with three openings: the central, wider one was used for the passage of wagons, while the side ones served as crosswalks. In Roman times the outer gates of Porta Praetoria were barred by portcullises that guarded the city. The two defensive turrets flanking the structure date to the same period, although they were reworked over time.

The forum and cryptoporticus of Aosta

The forensic complex of Augusta Praetoria was located at the intersection of the decumanus maximus and the main cardo. This area was characterised by a natural slope of the ground from north to south, and it became necessary to build a terrace to fill the gap. On its top was therefore located the sacred area, near which there were twin temples probably dedicated to Rome and Augustus, while in the lower part was the square used for public functions.

Roman Aosta
Remains of the Roman Forum used for public functions.

The worship area was bordered by a cryptoporticus, still almost entirely preserved. This is a basement gallery about two hundred meters long and arranged on three sides, with a double corridor of lowered arches made by means of travertine pillars and barrel vaults. The cryptoporticus functioned, it is assumed, as a warehouse for the goods of the stores and tabernae that faced the forum. Above it was a fine marble colonnade that framed the temples.

Roman Aosta
The forensic cryptoporticus of Aosta

The ludi area in Roman Aosta

In the northeastern part of Augusta Praetoria was the city area designated for the ludi. It included a monumental theater, which could seat up to four thousand people, and an amphitheater.

The Roman theater of Aosta

Aosta’s Roman theater is not contemporary with the founding of the city by Augustus but belongs to a later period, probably coinciding with the mid-1st century.

Of the original structure, the southern facade has survived in exceptional condition. It provides numerous clues as to what the theater could look like two thousand years ago. Firstly, the entire cavea was enclosed within a building more than twenty meters high and, most likely, provided with a canopy (theatrum tectum) to protect spectators from the winter snow. The southern facade, articulated by massive vertical buttresses, and made of large stone and travertine blocks, is externally finished in rough ashlar. The lower level, marked by a series of round arches, is overlaid by three orders of windows. To get an idea of the grandeur of the building, it is enough to consider that the summa cavea reached up to the level of the upper openings. Only the foundations remain of the stage portion, but it is known that it had a façade adorned with Corinthian columns, marble and statues.

The city’s amphitheater was located near the theater. Only some arcades are preserved, that are today included in a religious building in Aosta: the convent of the Sisters of St. Joseph. The scholars argue that the amphitheater could host about fifteen thousand people since it ha two tiers of bleachers. There is a controversy whether it was part of the original urban plan of Augusta Praetoria or it was built in later decades.

Samuele Corrente Naso


Appolonia, L., Fazari, M.C., Il Teatro romano di Aosta, Aosta, 2005.

Promis, C., Le Antichità di Aosta, Torino 1962, ristampa anastatica, Sala Bolognese, 1979.

Zanotto, A., Valle d’Aosta antica e archeologica, Aosta, 1986


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Samuele is the founder of Indagini e Misteri, a blog on anthropology, history and art. He has a degree in forensic biology and works for the Ministry of Culture. For pleasure he studies unusual and old-fashioned things, such as uncertain symbolism or enigmatic apotropaic rituals. He pursues mystery through adventure but that, inexplicably, is always one step further.

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