About 130 centuries ago, superb artists of the Magdalenian period left marvelous paintings on the limestone walls of caves deep in the mountains, including the cave at Niaux, whose artwork is known world-wide. Megaliths such as the dolmens of Tignac and Merens indicate the presence of humans in the valley around the third millennium BCE. Sometime in the third century BCE, the Celts began to settle here. The ruins of pre-Roman baths were discovered near the Couloubret establishment, indicating that the attraction of the Ax-les-Thermes hot springs is very ancient. During the great invasions, the mountains were a refuge for people from the piedmont.
They were also the scene of martyrdom. On May 11, 452, the future Saint Udaut was imprisoned in a barrel spiked with nails and thrown into a ravine at Ax by Valamir, the Ostrogoth king of Attila's army. Around 715, Arab tribes controlled all the passes of the Pyrenees. They crossed the Puymorens pass and occupied the town of Ax. They made their headquarters south of the town at Castelmau (Castle of the Moors). The earliest documents indicating the existence of towns and villages date from the ninth and tenth centuries. The eleventh century saw the establishment of the county of Foix, which included the collegiate parish of Sabarthès made up of the area known today as the Valley of Ax. The first feudal castles were constructed in strategic positions. Lordat was the most powerful, Castelmau protected Ax.