The Ukrainian province of Donetsk is one of the largest salt mining regions in the world. But that's not all. It also boasts a unique underground sanatorium for people with asthma and other lung complaints.
The sanatorium is basically made up of salt caves. Patients move in for weeks at a time. The caves are 300 meters below ground. Patients are only allowed to leave and go out into the daylight twice a day. The temperature in the caves is pretty low, so it's important to keep active. Soccer has become particularly popular among patients!