Sandanski Mineral Springs

Sandanski, in the Struma valley of southwestern Bulgaria and known until the 20th century as Sveti Vrach, sits above a field of more than 80 mineral springs across its municipality, roughly 20 of them within the town itself, ranging from 42°C to a hyperthermal 81°C. The water is hydrocarbonate, siliceous, sulphate-sodium and fluorine-bearing. An 1891 Ottoman-era account describes a vaulted stone bathhouse already serving the sick at the springs. Combined with the region's exceptionally low airborne allergen count and the highest average annual temperature in Bulgaria, the mineral water supports a specialised rehabilitation hospital focused on respiratory disease, and the town's many hotels — including large state-era complexes built to serve mass balneological tourism — draw their pools directly from the same municipal spring network.