Following a north-south axis, the city of Nîmes occupies the southern slopes of a group of hills and limestone plateaux near a small river, the Vistre. The Nîmes area was occupied from the Upper Palaeolithic (15,000 years ago) and several Neolithic sites are known within the current city limits. Nonetheless, it was not until the 6th century BC that the first village was established on the southern slopes of Mont Cavalier, at the foot of which the Fontaine spring emerges. During the 4th century BC, this oppidum, the principal settlement of the Volques Arécomiques, was surrounded by a wall enclosing around 30 hectares, and dominated by an imposing observation tower, the Tour Magne. The plain was crossed by numerous roads and trails linking a network of farms and funerary enclosures and leading to the other coastal oppida and trading posts of the region.

During the 2nd and 3rd centuries BC, the economic and demographic growth of the city, then part of the first Gallic province under the control of Rome, Gallia Transalpina (which under Augustus became Gallia Narbonensis), is shown by an extension of the inhabited area to the south and east, a little beyond its former limits. The penetration of Latin culture occurred rather slowly through, for example, the progressive introduction of new architectural elements (tile roofs, painted plaster). On the outskirts of the city, small groups of tombs lined the roads. In the countryside, large farms were established. They covered several hectares and crops such as grapes were grown. At the end of Caesar's reign (44 BC), the city of Nîmes became a Latin colony, Colonia Augusta Nemausus, to which 24 minor towns were attached.

In Nimes, as in many of cities of the Narbonne region, the Augusto-Tiberian period (27 BC to 37 AD) marked a radical transformation of the urban landscape. A new vast wall was constructed. Six kilometres long and enclosing nearly 220 hectares, it was interrupted by monumental entrances, such as the Augustus Gate by which the Via Domitia entered the city. A mint produced bronze and silver coins, including asses with a crocodile and the legend COL NEM. Two public areas, dedicated to the imperial cult, were constructed, a sanctuary (Augusteum) around the Fountain, and the Square House, built on the southern side of the forum. The city of Nemausus was soon equipped with an aqueduct which brought water from the Eure spring near Uzès. The urban expansion continued and the end of the 1st century was marked by a new phase of major public works with the construction of public baths and an amphitheatre (the Arena). In the private districts, houses with courtyards displayed varying degrees of material wealth. In the country to the south, a network of small farms with central courtyards developed.

The 2nd century, a period when the houses were permanently occupied and their interior decoration sometimes enriched, was the time of maximum extension of the city. Meanwhile, at the end of this century, the outskirts of the city were progressively abandoned, perhaps due to a decrease in population and lack of investment. This process was accentuated at the end of the 4th century, and especially during the 5th, ending with the abandonment of vast zones of the city and the destruction of major monuments. The city was eventually reduced to the area around the amphitheatre in the sector of the future medieval city (the Ecusson). At the end of the 5th century, its total surface was less than 20 to 30 hectares. The peripheral areas were devoted to farming or left fallow.