The 2000-year-old Salina Turda salt mine in Transylvania has been used as a theme park and museum since 1992.
Attractions include ferris wheels, spas, and an 80-seat amphitheater, as well as bowling and mini-golf facilities.
The mine originally closed in 1932. Before being turned into a theme park, it served as a shelter during World War II, and as a cheese storage site.
The salty air is also said to help visitors with lung conditions.