The town of Kyustendil, with its fertile plain and thermal springs, has attracted conquerors since Thracian times. It is situated 87 km southwest of Sofia, at the foot of the northern slopes of Ossogovo Mountain at an altitude of 530 m above sea level. Its climate is transitionally continental with a marked Mediterranean influence. There are 40 mineral springs with an average flow of 4 000 litres a minute and a temperature of up to 75°C. Being aware of the curative properties of their waters, the Romans developed this into the "town of baths". The weakly alkaline mineral waters are rich in sulphates, sulphides, hydro carbonates, etc. the spa is famous for the excellent results in the treatment of sterility and gynecological conditions, diseases of the peripheral nervous system, skin and chronic inflammatory diseases, and degenerative disorders of the joints as well as the heavy-metal poisoning that is an occupational disease for certain miners.

      The best Spa hotel in Kyustendil is the five-star Strimon Spa Club.