A spa town is a resort town based on a mineral spa (a developed mineral spring). Patrons visit spas to "take the waters" for their purported health benefits. The word spa is derived from the name of Spa, a town in Belgium.
Thomas Guidott set up a medical practice in the English town of Bath in 1668. He became interested in the curative properties of the hot mineral waters there and in 1676 wrote A discourse of Bathe, and the hot waters there. Also, Some Enquiries into the Nature of the water. This brought the purported health-giving properties of the waters to the attention of the aristocracy, who started to partake in them soon after.