The cathedral of Santa Maria Assunta and the collegiate church of Sant’Orso are the two greatest monuments of sacred art in the Aosta Valley, and they resemble each other in a curious way: both keep their finest piece somewhere you would never look. At Sant’Orso it is above the vaults. Here it is above the vaults and under your feet.
Warning: the treasure museum and the frescoes open only at the weekend. Outside 11 July to 6 September you get in only on Saturdays and Sundays, from 15:00 to 17:30, with the volunteers of «Chiese aperte». The cathedral itself is open and free every day, so the risk is not finding the door shut: it is walking in, going round the nave, coming out satisfied and never knowing that the three best things were ten metres away and out of reach.
A national monument since 1940, the cathedral has a history more than a thousand years long that can be read only by assembling the pieces, because every age has had a hand in it.
Two bell towers, and a façade that tells you nothing
From the square the cathedral disappoints, and it is better to know that in advance. The front is a neoclassical backdrop, and the real building begins behind it.
Walk round and look up: two Romanesque bell towers appear with their stone spires and two-light windows, one on each side of the church, and between them the lose roofs. Those two towers are the only thing that declares the building’s age from outside. They come from the same season that produced the roof-space cycle, from the works bishop Anselm I began between the end of the 10th century and the beginning of the 11th.
Inside, the nave is that of a large Gothic church turned over more than once, with its groin vaults and the choir at the far end. And it is in the choir that the interesting part begins.
The choir mosaics, which you look at by lowering your head
How many floors do you know that are worth a journey? In the upper choir of the cathedral there are two, and they belong to two different periods.
The first is 12th century and shows the months of the year. It is the commonest theme in Romanesque sculpture and mosaic, the calendar of labour: pruning, harvest, vintage, the killing of the pig. It was there to say that the time of the church and the time of the fields were the same time, and that the liturgical year turned along with the farming year. For the faithful of an Alpine valley, where the good season is short and every week counts, that was not abstract theology.
The second is 14th century and changes register: it shows real and fantastic animals together with the rivers Tigris and Euphrates. Two of the four rivers of the earthly paradise, which is the signal that this floor represents not the world but the garden the world began in, populated by beasts that live together without devouring one another.
Set side by side, the two mosaics record two opposite ways of looking at creation two centuries apart: the calendar of work and the garden of the origin.
The second Ottonian cycle, the one hardly anybody mentions
Above the vaults of the cathedral runs a cycle of 11th-century frescoes contemporary with the one at Sant’Orso, commissioned by the same bishop and preserved for the same reason: when the vaults were built lower than the roof, the painted band was sealed into a loft.
The subjects, though, are different, and that is what makes seeing both worthwhile. At Sant’Orso there are stories of the apostles and gospel episodes. Here there are the ancestors of Christ, the bishops of Aosta, the stories of Saint Eustace, the Roman soldier converted and later martyred, and the stories of Moses. A dynastic and biblical programme with the line of bishops inside it: the patron placing himself and his predecessors on the same wall that tells the Bible.
Together, the two cycles make Aosta one of the principal centres of Ottonian painting in Europe. That is not a brochure formula: very little 11th-century mural painting has reached us anywhere in Europe, and almost none of it in this state.
Warning: do not confuse the two Anselms. The patron is Anselm I, bishop of Aosta between 994 and 1026, not Anselm of Aosta, the philosopher who became archbishop of Canterbury and who was born in the city around 1033, after the bishop’s death.
Saint Gratus, the head in the well and the jawbone that came away
Now the best story, and it has to be told for what it is: a legend written down in the 13th century, not a fact.
The account says that Saint Gratus, bishop of Aosta, found in Palestine the head of John the Baptist, thrown into a well after Salome had asked for his beheading. Gratus carried the skull to Rome to hand it to the pope and, at the moment he offered it, the jawbone came away and stayed in his hand. The event was read as a divine sign, and the jawbone followed Gratus to the Aosta Valley, where it has remained.
It will sound like folklore, and yet it has material consequences you can still see. The jawbone is kept in a head-shaped reliquary commissioned for the cathedral by François de Challant in 1421: goldsmith’s work of that quality, in an Alpine diocese, is explicable only by the prestige of the relic. And Saint Gratus is still the patron of Aosta.
The church also holds a 15th-century painting of the stories of Saint Gratus in which the scene of the handing over reads perfectly: the kneeling bishop offering the skull, the pope enthroned, the clerics gathered round.
The treasure museum, which sits inside the church
Why does an Alpine diocese own goldsmith’s work of this quality? The Treasure Museum of the cathedral opened in 1984 and is laid out in the ambulatory and the nearby relics chapel: it is not a separate building, it is the church opening its own cupboards.
It gathers a survey of Aosta Valley art from the 13th to the 18th century, putting together pieces from the cathedral treasury and works brought in from parishes across the valley. Goldsmith’s work, reliquaries, sculpture, vestments. It is a small museum, half an hour will do it, and its quality rests on a precise historical fact: the Aosta Valley was a corridor towards France and Burgundy, so models and craftsmen arrived here that the rest of Piedmont never saw.
Anyone with the treasury of San Lorenzo cathedral in Genoa in mind will find here the Alpine version of the same idea: a treasury that is not a list of precious objects but an account of what a diocese thought worth keeping.
The crucifix that came from the arch of Augustus
One piece is worth hunting down on purpose, because it ties this church to another monument in the city. The wooden crucifix hanging under the vault of the arch of Augustus, at the end of the street towards the bridge, is a copy. The original was placed there in 1449 as a votive offering against the flooding of the Buthier torrent, and it is kept here today, in the treasure museum.
It is the kind of detail that changes a walk. You pass under the arch, you see the crucifix, you assume it has hung there for five hundred and seventy-seven years, and in fact the real object is in front of you in a case while the one out in the weather is its stand-in. I write about it at length in the piece on the arch of Augustus and the stone bridge.
Practical information
Details checked on 7 September 2026 on the website of Aosta cathedral and on the regional tourist portal. Prices and opening times change: check again before you travel.
Tickets. The treasure museum alone costs 4 euros. The ticket covering museum and 11th-century frescoes costs 5 euros. The cathedral is free and can be visited during church opening hours.
Opening times. The museum and the frescoes open Saturday and Sunday from 15:00 to 17:30, staffed by the volunteers of the «Chiese aperte» scheme. From 11 July to 6 September they open every day, again 15:00-17:30.
Free admission. Entry is free for children and young people up to 18, for students up to 25 and for holders of the museum pass.
Getting there. The cathedral stands in piazza Giovanni XXIII, at the centre of the Roman city, a few steps from the forum cryptoporticus: ten minutes on foot from the railway station. For information and special bookings, write to info@cattedraleaosta.it or telephone 347 734681.
How long it takes. A good hour for the museum, the frescoes and the choir mosaics; twenty minutes if you stay in the church. Bear in mind that the two-and-a-half-hour afternoon window has to be fitted around the guided visit to Sant’Orso, which leaves at 16:00: the two can be done in the same afternoon, but not by chance.
The rest of Aosta
Fitting the weekend afternoon window into a single trip is this city’s practical problem, and I take it on at length in what to see in Aosta in one day. The other 11th-century cycle, the contemporary one by the same bishop, is in the collegiate church of Sant’Orso, the cloister and the forty capitals. The other pieces in the cluster are the Roman theatre and the walls of Augusta Praetoria, the megalithic area of Saint-Martin-de-Corléans and the arch of Augustus with the stone bridge.
If Ottonian art interests you, that moment when the empire looked to Rome and to Byzantium at once, its capital is Aachen, where the palatine chapel and the imperial treasury set out the world bishop Anselm belonged to.
Photo credits: mosaic floor by Rufus46 (CC0); bell towers, 11th-century fresco, stories of Saint Gratus and choir stalls by Laurom (CC BY-SA 3.0). All from Wikimedia Commons.
