The Bridge of Gran Arvou spans the Rû Prévôt irrigation canal, and includes a large corridor covered by flagstones.
The Grand Arvou is an arch bridge, with a span of 68.5 m and an elevation of 13,60 m between the arch's top and the ground; the distance between the roof and the base of the arch is 10,5 m. The bridge is built in mortar and small incoherent stones, with partial plastering. The plan is irregular, with a general trapezoidal shape, but without the main parallel side; the walls's thickness varies from 50 to 55 cm. The roof is covered by flagstones, which helped it resist to the centuries.
In the late 13th-early 14th century, there was a series of programs aiming to improve the irrigation level in Aosta Valley, due to increased demand of animal husbandry. One of this was the construction of canal, the Rû Prévôt, by will of Henry of Quart, provost (hence the name) of the Aosta Cathedral. This included also the couple of bridge-aqueducts which are now visible.
The income of the canal exploitation was later acquired by the Dukes (later Kings) of Savoy. In the 20th century, the canal was mostly channeled into pipes.References:
The Amphitheatre of the Three Gauls was part of the federal sanctuary of the three Gauls dedicated to the cult of Rome and Augustus celebrated by the 60 Gallic tribes when they gathered at Lugdunum (Lyon). The amphitheatre was built at the foot of the La Croix-Rousse hill at what was then the confluence of the Rhône and Saône.
Excavations have revealed a basement of three elliptical walls linked by cross-walls and a channel surrounding the oval central arena. The arena was slightly sloped, with the building"s south part supported by a now-vanished vault. The arena"s dimensions are 67,6m by 42m. This phase of the amphitheatre housed games which accompanied the imperial cult, with its low capacity (1,800 seats) being enough for delegations from the 60 Gallic tribes.
The amphitheatre was expanded at the start of the 2nd century. Two galleries were added around the old amphitheatre, raising its width from 25 metres to 105 metres and its capacity to about 20,000 seats. In so doing it made it a building open to the whole population of Lugdunum and its environs.