The Pont du Gard is a Roman aqueduct which was built to supply water to one of the large Roman towns in the area (I can't remember which one). It's a very impressive construction, and appears almost completely intact.

It's a short drive from Avignon, and once there the site is easy to walk around. There's a bit more of a scramble up the hill if you want to get to the top from where you can look along the top of the aqueduct.

It was a blazing hot day when we went there, and we had a picnic sitting on the banks of the river, with the marvellous vista of the aqueduct in the background. There were quite a few tourists at the site, but a five-minute walk down the river got us away from everyone.

It is a truly magnificent sight. This is a must see if you're in the area.