Criptoportico forense di Aosta

Beneath the quiet garden of Piazza Giovanni XXIII lies one of the most evocative survivals of Roman Aosta: a semi-subterranean gallery that once embraced the sacred terrace of the colony's forum. Dim, cool and remarkably intact, it lets visitors stand inside the structural skeleton of a Roman city centre almost unchanged since antiquity.

Why it matters

The cryptoporticus surrounded the sacred area at the heart of Augusta Praetoria, where two twin temples stood on a raised platform. Its double barrel-vaulted corridors did serious engineering work: they braced the sloping ground on which the sanctuary was built, while providing a covered ambulatory. Because the later city grew above it rather than through it, the structure survives with an immediacy that few Roman monuments anywhere can match. The Ministry of Culture describes it as one of the best-preserved remains of its kind, and walking its length is the closest any visitor can come to experiencing the civic centre of the colony as the Romans framed it.

What to notice

The building is roughly quadrangular in plan, with three wings arranged in a horseshoe; internally each is divided into two parallel aisles separated by arcades resting on sturdy piers of squared tuff blocks. The central gallery runs about ninety metres, the side wings around eighty-six each. Look up for the small wolf-mouth windows, which slice thin beams of daylight across the vaults; and look at the fine plaster facing still clinging to the masonry, evidence that this was never a rough service space. From the garden above, remains of the twin temples are visible at the centre of the former sacred area.

Context and history

Scholars generally place construction in the decades straddling the era change — the late first century BC running into the early first century AD — within the first generations of the colony founded in 25 BC, making it contemporary with the founding programme whose walls and gates still frame the centre. The cryptoporticus supported the temple terrace that dominated the forum, the political and religious heart of Augusta Praetoria. Its afterlife is equally significant: around AD 380–400 the first cathedral of Aosta was built against its eastern wing, anchoring the new Christian centre physically to the old Roman one — a relationship still legible today, since the Cathedral and its medieval cloister stand directly beside the site. The gallery remained buried and structurally sound through the centuries, which is precisely why it can be walked now, plaster facing and all.