Rich in active gases or metals — a strong mineral character.
Buoyancy
Standard buoyancy
LowHigh
Soft water — natural, classic buoyancy.
SoufreSulfuresSulfates
Naftalan, in central Azerbaijan, is one of the world's most singular spa destinations, where the signature medium is not mineral water but a specific crude naphthenic oil found only in this locality. The petroleum, drawn from shallow deposits, is used in warm immersion baths within a long thermal tradition. Naftalan was a prestigious Soviet-era health resort visited by millions, and its unusual ritual — immersing the body in warm petroleum — has no equivalent anywhere else on Earth, making it a globally unique balneological phenomenon.
Insider tip — Naftalan's petroleum baths are a globally unique curiosity that has survived into the 21st century as a functioning resort, drawing visitors from across the former Soviet space for its singular naphthalan crude oil sessions. The warm brown oil at 37°C coats the skin and must be washed off thoroughly afterward. A museum of empty bathtubs displays discarded crutches and walking aids left behind by former patients. The town's sanatorium architecture, a frozen mid-century aesthetic, is worth exploring even outside of treatment hours.
