Nîmes is a very recent entry to the French T-list, thus one can assume that there are plans for a nomination within the next years. Nîmes is also part of the T-list site “Les villes antiques de la Narbonnaise et leur territoire”, but there is probably little confidence in a proposal that only includes the Roman heritage. So the approach has been extended to the entire historic city centre with a medieval cathedral and buildings and mansions from the 16th to 19th century. In the description on the WHC website Nîmes is referred to as an example of the influence of Roman architecture on urban planning and architecture of later epochs until today. Stylistic and decorative elements from the ancient times were also used in buildings of the later centuries.
Undoubtedly, the Roman remains are the most important monuments in Nîmes. First the amphitheater: it is very similar to the Arena in Arles, but more complete and better preserved. Second the Maison Carrée: I was even more impressed by this well preserved Roman temple. The Corinthian columns correspond nicely with the modern Carré d'Arts by Norman Foster on the opposite side of the square (photo). The temple is completely preserved, due to the almost uninterrupted use as a church, later as meeting place for the senators, a barn during the French Revolution, an archive and finally a museum. Other Roman remains are the Temple of Diane and the Tour Magne (both in the Jardins de la Fontaine), the remains of the Roman city wall (Porte Auguste, Porte de France), and the Castellum, a circular tank and the endpoint of the Nîmes aquaduct.
The narrow streets in the old town north of the Amphitheatre are also worth to explore. In the area around the Tour d'Horlange and the Cathedral are many mansions with wrought-iron balconies and adorned portals, most of them dating from the 17th to 19th Century. Where possible, you should have a look in the courtyards, some have beautiful staircases.
However, I have some doubt that the concept of a stylistic relation between the Roman remains with later architecture is really convincing and that an inscription would be justified. Nevertheless, Nîmes is worth a detour, if you have some time left after visiting the four WHS in the region. It can easily be visited in a half day from Arles or Avignon.