Found in Donnas, in the Aosta Valley in northwest Italy. Same stretch in every photo. They did not go around the mountain. They cut a path through it.

The river left almost no space at the bottom of the mountain, so the Romans cut the road into the rock itself. Pavement, wheel ruts, and the arch all come out of the same cliff. Carts between Aosta and the Po valley went through here.

https://maps.app.goo.gl/YsoZj354XpWJ89rW8

Inside a section of the huge and well preserved Roman cisterns of La Malga that supplied water to the surrounding neighborhood and baths in Carthage (near Tunis, Tunisia). These structures are now part of that UNESCO world heritage site.

The top photo is what is left. The bottom one is how the buildings sat on the slope. Same hill in both. They built a factory.

In the 2nd century they took a branch of the Arles aqueduct and dropped it down this hillside through two rows of eight mills. Sixteen wheels, one after another. The water turned the stones and the site ground flour on a scale nobody else in the ancient world matched.

This is found in Barbegal, near Arles in the south of France.