Figure 2 is a photograph of the Pont du Gard revealing that the bridge spans a river valley and is made up of three tiers of arches. The bottom tier contains at least 6 arches, each 25 metres wide and one spans the river. The middle tier is made of at least 9 arches. They are the same size as the ones below, but more are required to cross the valley at that height. The top tier is made of about 30 much smaller arches which support the aqueduct. The bridge was designed to carry water and is not much wider than a footbridge. The bridge is 50 metres high, estimated to weigh 50,000 tonnes and uses 20,000 cubic metres of soft yellow limestone blocks, taken from a nearby quarry that borders the river.

 1.2.1 The Pont du Gard: one of a kind