The Gauls consular road, built by the Romans to link Rome to the Rodano Valley, has one of its most characteristic points in the Donnas section, which is dug into the live rock over a length of 221 metres.

The dimensions of the excavation are highlighted by the rocky headland that has been left, within which an arch has been dug out: it measures 4 metres in width, 4 metres in height and the distance between the two jambs is almost three metres: during the Middle Ages it was used as the gateway to the Suburb, which was closed during the night.

On the pavement of the road you can still see the furrows left by the carriages, while a little beyond the arch there is milestone on which the number 36 represents the distance between Donnas and Aosta in miles (approximately 50 km).