SPA, a town, of Belgium, lying less than 20 m. S.E. of Liége and in the same province, famous for its mineral springs, which are reputed to be the oldest known in Europe, having been first discovered in 1326. They are supposed to have given the common name of “spa” to such resorts. The town is situated 850 ft. above sea-level and the heights above the valley reach 1100 ft. In the 18th century it was the most fashionable resort in Europe for the medicinal use of such waters, being visited by Peter the Great of Russia, Gustavus III. of Sweden, and Joseph II. of Austria. In 1807 much of the town was burned down, while the principal buildings, the Casino and the Pouhon, are quite modern. Spa has not held its own with its many French and German rivals, but it still attracts about 20,000 visitors annually. Pop. (1904), 7759.