The Pont du Gard is a Roman aqueduct crossing the Gardon river in southern France, and it represents the least showy but most characteristic side of Roman architecture — infrastructure engineering. Here the aim is not a temple or monument but to carry water from one point to another; the form arises entirely from that function.

The structure is only one piece of an aqueduct roughly 50 kilometres long, and it is made of three tiers of arches stacked one above the other: wide, large-span arches cross the river below, while ever-smaller arches above hold the channel aloft. The total height reaches 49 metres. The ashlar blocks of the lower two tiers are laid without mortar — cut precisely and fitted together by dry stacking alone; some blocks exceed six tonnes. The bosses left for the cranes to grip and the worksite marks are still on the stones.

The real engineering is in the invisible part: the gradient of the channel at the very top was set to fall only a few centimetres per kilometre across the whole 50 kilometres — so the water flows by gravity alone, continuously but without overflowing. The Pont du Gard thus unites the repetition of the arch, dry-set stone stacking, and hydraulic precision; its survival for 2,000 years is proof of the durability of Roman infrastructure architecture.