Dax is a commune in Nouvelle-Aquitaine, southwestern France, sub-prefecture of the Landes department. It is known as a spa destination…Dax is a commune in Nouvelle-Aquitaine, southwestern France, sub-prefecture of the Landes department. It is known as a spa destination, specialising in mud treatment for rheumatism and similar ailments. Dax is also known for its bullfighting culture, especially during the August ferias, one of the most crowded festival events in France with 800,000 people attending over five days. It is also a market town, former bishopric and busy local centre, especially for the Chalosse area.