Upperhanded

What turned out to be a very rewarding stopover (in thermal experience sense that is), a visit to Ax-les-Thermes should be high on your hot springs agenda.

The town itself is not too different, especially during the afternoon, very sleepy. However authorities have gone out of their way to make the thermaility of the surroundings as the an example of why you would want to stay here. The village's existence is primarily thanked to this thermaility.

Some publicly accesible bassins have been constructed to enable enjoying the hot springs as well being an attraction in their own right.

Ax-les-Thermes history is very much entwined with it's thermal heritage. Wikipedia:

'The waters, which were used by the Romans, were historically claimed to treat rheumatism, skin diseases, and other maladies.[4] The springs were developed in the medieval period on the orders of Saint Louis to treat soldiers returning from the Crusades afflicted with leprosy. From the 19th century, a spa tourism industry developed'.

The village of 1200+ inhabitants relies very much on hydrotherapy. Again Wikipedia:

'Hydrotherapy (there are 60 sources at temperatures ranging from 18 to 78 °C, feeding three spas: Couloubret, Modèle, and Teich. The waters treat especially sciatica, rheumatism and certain respiratory diseases), winter sports, and tourism in general'.

The Commune website of Ax-les-Thermes with respect to it's heritage:

'In 1241, probably to compensate for the damage caused by a fire, the Count of Foix granted extensive tax privileges to Ax. It only became more popular and space within the walls became scarce. The freely available waters of Ax were used to wash wool, to scald pigs, to make soup, to treat people. The districts of the steam baths were not of good reputation: beggars, acrobats and girls of joy held the upper hand there'.

If my info is correct there are two commercial facilites. 

Thermes du Teich is one (above with park, below), Google reviews amount to 4.4 stars.

Les Bains du Couloubret (below) seems the more popular, Google: 4.2 (3,200+ reviews), Tripadvisor 4 stars (780+ reviews) while Facebook gives 4.5 stars (960 reviews).

Nature & Sources Chaudes probably has the go-to info (Jul. 5) on all the thermal qualities of Ax. It includes a map of the town with the various locations of thermal interest, though not all the mentioned 63 springs.

Highlighted are La fontaine du Couzillou, Le bassin de la Basse, Le bassin des Ladres, La source des Canons, La source des Rossignols, La fontaine du Coustou, La fontaine des Neiges and Le bassin de l'Axéenne.

Finally, another reference, Kucavana (31 Oct. 2020):

'Ax les Thermes is a spa town. I don't think we've ever seen a city with so many pools and hot springs before. It is an incredible place, every two steps you come across a fountain or a small pool of sulphurous waters.

The waters of these natural thermal pools in the south of France are hot all year round and are located in an incredible place in the middle of the French Pyrenees.

One of the most symbolic hot spring pools in the city is le Bassin des Ladres, in front of an old hospital for lepers that has a pond at the entrance to the thermal waters where you can put your feet. It is not uncommon for visitors to the town to refresh their tired feet on it after a long walk or in the attached hot springs of sulfur .

Apart from this natural thermal pool, there are two more significant ones. Behind the casino and that of a large square near the river'.