The Castellum Aquae marks the arrival point of the Roman aqueduct that once supplied the ancient city of Nemausus. Built in the 1st century AD, it distributed water throughout the city after a journey of nearly 50 kilometers from the Eure spring near Uzès. This aqueduct—whose most famous section is the Pont du Gard—ended here.

Though discreet today, this site was once essential to the daily functioning of the city.

A remarkably precise engineering system

At the center is a circular basin about six meters (about 20ft) in diameter, carved directly into the rock. Water arrived through a channel and was then distributed with impressive precision.

Around the basin, ten openings supplied different parts of the city through pipes. A valve regulated the flow, while drainage outlets at the bottom handled overflow. Together, this formed a complete system capable of supplying baths, fountains, homes, and the city’s drainage network.

What you can see on site

The visit is brief but rich in detail. The stone basin is clearly visible and well preserved, including its inner rim. The distribution openings can still be seen around the edge, arranged in a fan-like pattern.

You can also identify the water inlet, carved into the stone, as well as the drainage outlets at the bottom. The entire structure sits within a natural rocky hollow, showing how Roman engineers worked with the landscape.

A rare site in Europe

This site stands out for its level of preservation. Very few structures of this kind remain visible today, and even fewer in such a readable state. The Castellum Aquae of Nîmes is one of the rare places where you can clearly understand how water distribution worked in a Roman city.

Rediscovered in the 19th century and later protected as a historic monument, it remains a valuable testament to ancient engineering.

An easy site to miss

To be honest, this is the kind of place you can walk past without noticing. It’s only about a ten-minute walk from the Arènes de Nîmes, but the site is set slightly back in a small courtyard. It’s easy to pass right by without seeing it. There is an information panel on site, but you do need to stop to take it in.

Why it’s worth the stop

This isn’t a spectacular landmark, but it changes how you see the ancient city. In just a few minutes, you understand how water arrived, circulated, and was used in everyday life.

That contrast is part of what makes it so interesting: an essential site that remains almost hidden. Knowing it’s there, just steps from the major monuments, adds a deeper, more practical layer to your understanding of Nîmes.