An inscription on the north side says who paid for it: Gaius Avillius Caimus of Padua, one of the operators of the mine nearby, out of his own pocket, in 3 BC. The word PRIVATVM sits at the centre of the text, and it is easy to see why he cared.
What to see
The bridge is 60.46 metres long and 2.26 wide, and crosses the gorge of the Grand Eyvia at the only point where crossing was possible: here the ravine narrows to twelve metres but drops 66. Its single arch spans 14.24 metres. On the lower level runs a corridor 50.35 metres long, used to check that the water channel above was watertight: two rows of small windows light it, the lower ones on the floor and the upper ones on the roof, so that the keeper could spot leaks at once. There were probably three levels originally, giving a total height of 22.15 metres.
Visiting
A footpath now runs along the channel that once carried the water. For centuries the bridge was believed to have carried iron ore; the full survey by Mathias Döring in 1996 showed instead that it was part of an irrigation conduit six kilometres long, bringing water to the fields of the new colony of Augusta Praetoria and to a washing plant for the ore mined at Cogne.
Our editors' tip
You go through it, not just past it: the inspection corridor is the part that stays with you, and from there you look at the gorge the way the Roman maintenance man did. If heights bother you, know in advance that there are 66 metres below.