Dax (formerly called Acqx), a French town and watering-place in the department of Landes, on the left bank of the Adour. It was a Roman station, and the old town is surrounded by ramparts, which are in part Roman. The modern suburb Sablon is on the other side of the river, and is joined to the old town by a bridge. There is a castle, a church which was once a cathedral, and a bishop's palace now used for municipal purposes. The town produces stoneware and liqueurs, and it has thermal springs useful in rheumatic disorders.