Nimes was founded as the Roman colony of Nemauses. A mere 15 years of surviving Caesar's campaigns along the Nile would get you a retirement estate in the vicinity of Nimes. So since all the early Roman colonists were veterans of the Nile wars, the crocodile (and the palm tree) became the symbol of Nimes.
The rest of the Roman legacy is pretty obvious too. Nimes' arena is the star attraction in the city. It's probably better preserved than any other we've visited including those in Rome and Verona. We drove into Nimes on a day trip from Arles. We wandered through much of the city center but the arena was the only place we really found a crowd.
There's a slightly confusing pre-marked path to follow if you take the audioguide tour of the arena. It winds in and out of the center and the various levels and is actually fairly informative. There are also some nice views over the town from the top of the arena seating.
Nimes has a few other attractions associated with the Roman days. The Maison Carree was so thoroughly scaffolded and draped in giant 'coming soon' banners that we didn't even bother to take a picture of it. During our visit, it was transformed basically into a movie theater showing some sort of history of Nimes. A little disappointing actually for a historic landmark. The center of Nimes has a lot of cafes and shops strewn through the pedestrian sections. As this picture shows though, it was more or less deserted on a weekday afternoon.
Just a few miles north of Nimes is the Pont du Gard. This is a view of the Gard from atop the bridge itself. There are visitor centers on both sides of the river so it doesn't really seem to matter which side you arrive on since you can freely cross the bridge. We parked on the west bank which has a parking fee until 19:00 at which point it becomes free. So we sat outside the gates for about 5 minutes until we were sure it was 19:00 and then visited. Kind of a strange system.
As Roman ruins go, this is definitely one of the more spectacular ones we've seen. At the top level was part of the 50 kilometer-long aqueduct from Uzes to Nimes. This was built sometime in the 1st century BCE and while some sections are in a bit of disrepair, it's really quite impressive how much is original. The Romans took into account the possibility of flooding control - something the medieval engineers in Avignon never seem to have mastered. It's a little hard to tell in this picture but the Gard River is over there in the right-most arches of the bridge.
There are trails throughout the area along both banks so you can view the bridge from just about any angle you'd like. It appears that swimming in the Gard downstream of the bridge is also popular, although not in May when there is still snow nearby.