Built on a site populated as early as the copper age, Castelnau-le-Lez is more than 2000 years old.
In Antiquity, it was a fortress dominating the river Lez known as Sextantion or Suxtantione, 6th station on the Roman Via Domitia.
In the Middle Ages, the inhabitants regrouped at the foot of the « New Castle » - Castellum Novum – in order to protect themselves from the Barbarian invasions.
At that time, stone replaced wood for all types of building : bridges, castles, churches. These were then called « New bridge », « new castle », « lo castel nou » in occitan.
Over the centuries, the village gathered around its 12th century church.
Today, the town is organised around a pretty shopping square and on the banks of the river Lez.