# A prehistoric sanctuary under a city

> At Saint-Martin-de-Corleans in Aosta, a 10,000 sq m Neolithic sanctuary sits 6 meters below street level, under a Roman colony laid out in 25 BC.

URL: https://myitalia.it/stories/a-prehistoric-sanctuary-under-a-city
Last updated: 2026-09-02

Under the Saint-Martin-de-Corleans district of Aosta lies a prehistoric sanctuary of around 10,000 square meters, dug out 6 meters below the modern street level and in use from the late Neolithic to the early Bronze Age.

## 6 meters down, below the modern street

The excavated area covers around 10,000 square meters and sits 6 meters below the level of the road above it.

It was a sanctuary, in use from the last centuries of the 5th millennium BC through the early Bronze Age, then again in Roman times and in the Middle Ages. What came out of the ground is a ritual landscape: anthropomorphic stelae, ritual pits, alignments of wooden posts, dolmen tombs and cist burials.

The stelae are the part people remember. They are carved slabs with a human figure on them, standing in rows, and they were already old when the Romans arrived.

## The building above is engineered around the hole

The museum over the site covers 9,820 square meters and clears 46.5 meters in a single span.

That span is the point of the design. Nothing rests on the excavation, so the sanctuary can be read as one continuous surface rather than as trenches between pillars, which is how most urban digs end up being displayed.

## Three dates, one museum: 2016, 2023, 2025

The museum was inaugurated on June 24, 2016, reopened in November 2023 and took the name MegaMuseo in February 2025.

Three names for the same address in nine years is worth knowing before you search for it. Older guidebooks call it the area megalitica di Saint-Martin-de-Corléans, more recent ones the MegaMuseo, and both are the same place.

Here is the gap we could not close: hours and ticket prices are not published on any page we could read on valledaostaheritage.com. That is unusual for a site of this size, and it means you check locally rather than plan around a published timetable.

## 25 BC: a Roman colony dropped on top

Aosta was founded in 25 BC as Augusta Praetoria Salassorum, and its walls enclosed 414,128 square meters with 4 gates.

One of those gates, the Porta Praetoria, is still standing. So are the Roman theater, the forum cryptoporticus, the Roman bridge and the Arch of Augustus. The regional source describes the city as holding more visible Roman remains than anywhere in Italy except Rome, which is a popular formula rather than a measured ranking, and is worth treating as such.

The two things sit on the same ground. A colony was laid out in 25 BC over a sanctuary whose last use, in the early Bronze Age, was already ancient history by then.

## The Arch of Augustus argues with itself

The arch was raised in 25 BC for the victory over the Salassi won by Aulus Terentius Varro Murena, and its single opening measures 11.40 meters under the keystone.

Look at how it is put together and you find 10 half-columns with Corinthian capitals holding up a Doric entablature with metopes and triglyphs. Those two orders do not belong together in a textbook, and here they do.

It is the same year as the city walls, the same campaign, and the same military logic: build fast, build large, and let the details argue.

## What to read the site as

The sequence is the story: a sanctuary in use before 4000 BC, a Roman colony in 25 BC, a medieval town, and a modern district that put a road over all of it until the excavations went 6 meters down.

Nothing about the surface of Aosta tells you the sanctuary is there, and that is the whole reason it survived: a district built over a field, and a field that turned out to be a cemetery and a temple.

Read in that order, the 25 BC colony stops being the oldest thing in Aosta and becomes the middle chapter. The sanctuary was already out of use when the legions arrived, the Middle Ages built over it again, and only the excavation put the sequence back in view.

It also explains the shape of the visit. Roman Aosta is on the surface and you meet it by walking; the megalithic area is a single room you go down into, and the 46.5 meter span overhead is what lets you see it whole. For the wider region, see [Valle d'Aosta](/regions/valle-d-aosta).

## FAQ

### What is the megalithic area of Aosta?

A prehistoric sanctuary of around 10,000 square meters excavated 6 meters below the modern street at Saint-Martin-de-Corleans, inside Aosta. It was in use from the last centuries of the 5th millennium BC to the early Bronze Age, and holds anthropomorphic stelae, ritual pits and dolmen tombs.

### What is the MegaMuseo in Aosta?

The museum built over the megalithic area. It opened on June 24, 2016, reopened in November 2023 and took the name MegaMuseo in February 2025. The building covers 9,820 square meters and spans 46.5 meters without a support, so the excavation below is uninterrupted.

### How old is Aosta?

The city was founded in 25 BC as Augusta Praetoria Salassorum. Its Roman walls enclosed 414,128 square meters with 4 gates, of which the Porta Praetoria survives. The sanctuary under Saint-Martin-de-Corleans was already in use in the late 5th millennium BC, thousands of years earlier.

### What are the opening hours of the megalithic area of Aosta?

Not published anywhere we could read. No indexable page on valledaostaheritage.com carries hours or prices for the 10,000 square meter site, so check on the day or ask at the museum desk rather than planning a morning around a timetable you found on a third-party page.

### How tall is the Arch of Augustus in Aosta?

The single arch stands 11.40 meters under the keystone. It was raised in 25 BC for the Roman victory over the Salassi led by Aulus Terentius Varro Murena, and mixes 10 half-columns with Corinthian capitals under a Doric entablature.

## Sources

| Fact | Source | Confidence | Valid until |
|---|---|---|---|
| L'area megalitica di Saint-Martin-de-Corleans, dentro Aosta, e' un santuario preistorico di circa 10.000 metri quadrati scavato sei metri sotto il livello stradale: e' stato frequentato dagli ultimi secoli del V millennio a.C. all'eta' del Bronzo, il museo e' stato inaugurato il 24 giugno 2016 ed e' stato riaperto nel novembre 2023, assumendo il nome MegaMuseo nel febbraio 2025 | [Wikipedia](https://it.wikipedia.org/wiki/Area_megalitica_di_Saint-Martin-de-Corl%C3%A9ans) | medium | 2029-12-31 |
| Aosta nasce nel 25 a.C. come Augusta Praetoria Salassorum: la cinta muraria romana racchiudeva 414.128 metri quadrati con quattro porte, e la citta' conserva il maggior numero di resti romani ancora visibili in Italia dopo Roma | [Wikipedia](https://it.wikipedia.org/wiki/Aosta) | medium | 2099-12-31 |
| L'Arco di Augusto di Aosta fu eretto nel 25 a.C. per la vittoria romana sui Salassi guidata da Aulo Terenzio Varrone Murena: ha un fornice alto 11,40 metri sotto la chiave di volta e mescola dieci semicolonne con capitelli corinzi a una trabeazione dorica con metope e triglifi | [Wikipedia](https://it.wikipedia.org/wiki/Arco_di_Augusto_(Aosta)) | medium | 2099-12-31 |

## Image

https://media.myitalia.it/media/city.aosta.1600.jpg
Author: Krzysztof Golik. License: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0).
Source: https://commons.wikimedia.org/wiki/File:Town_hall_of_Aosta_(1).jpg

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