Built on the site of the ancient town of Pautalia, is one of the most famous Bulgarian resorts. It lies at the foot of Ossogovo Mountain at an altitude of 510-530 m. Thanks to the lush vegetation of the surrounding landscape and the beautiful gardens of its neat lovely houses, the town is refreshingly green and inviting.
The climate is traditionally continental with Mediterranean influence. The mild weather is largely due to the beneficial effect of the mountains which surround the plain from the north, east and west. The average annual temperature is 11C; and the average July temperature, 21.6C. The annual duration of sunshine is 2,200 hours on the average , and the relative air humidity, 68 per cent.
The mineral waters of the numerous fountains (natural springs and wells) have an almost uniform chemical composition, temperature and sulphide content (71-73C; 9.4-11.3 mg oxidable sulphur compounds estimated in terms of hydrogen sulphide). The waters are clear , colourless, with a pleasant taste and a slight smell of hydrogen sulphide. They are mildly mineralized, hyperthermal and contain sulphides, silicon (83 to 104 mg of metasilicic acid), fluorine (7.6-8.9 mg per litre) and sulphates of sodium with a strong alkaline reaction (pH 9.13-9.80). The total flow is about 2,400 l/min. Their curative and preventive properties are mainly due to the sulphides , the high metasilicic acid content, the high temperature, the hypotonic effect, the mild mineralization and the relatively high fluorine content.
The curative properties of Kyustendil's mineral waters have been known since ancient times. Another important curative agent, used for the systematic treatment of a wide range of diseases, is the peat mined near the village of Baikal which is reach in humic acids and organic substances. It is used in peat baths, for general and partial applications, vaginal and rectal electrophoresis, etc. The favourite climate, the curative peat from Baikal, the mineral waters and the possibilities of specific fruit-diet therapy attract many Bulgarian and foreign visitors to Kyustendil.