Photo Credit: Roadtrippers.com

Once underground mines have served their purpose, most are sealed and forgotten. The 2000-year-old Salina Turda Salt Mine in the city of Turda, Romania was no exception. The mine which is believed to have opened in the Middle Ages (as far back as 1075) was shuttered in 1932 after competition from neighboring mines rendered its operation unprofitable.

But fortunately, Salina Turda was not consigned to oblivion. In 1939, during World War Two, local authorities reopened the mine and used its massive underground caverns as bomb shelters for the residents of Turda. When the war drew to an end in 1945, local cheese makers decided to use the mine's naturally cool and dark interior for storing cheese.

Photo Credit: Roadtrippers.com

This continued until 1992, when the city's officials came up with the brilliant idea of turning the historical salt mine into a tourist destination featuring a museum for adults and an amusement park for kids. The fact that the mine had been equipped with electricity since 1910, and had water and waste pipes installed when it became a cheese warehouse made the transformation relatively easy. Their vision proved to be an enormous success. The theme park, which has been visited by over 2.5 million people since its opening, is now ranked 22 among the world's most spectacular destinations.

Visitors to the theme park are transported 400-meters (1,300 feet) underground aboard the same elevator shafts that were used to bring excavated salt to the surface over a century ago. Inside the massive cavern lies an amusement park like none other — One that includes a giant Ferris wheel, a mini-golf course with six different tracks, tennis courts and even an underground lake that can be navigated using paddle boats. To keep the amusement park's youngest visitors entertained, there is a special playground complete with slides and turntable baskets.

Photo Credit: Salinaturda.eu

And that is not all - The mine even has an 180-seat amphitheater that can be used for concerts and conferences as well as a swimming pool and spa for those that want a relaxing experience underground.

Adults and kids seeking something more cerebral can visit the museum and learn about the history of the mine while admiring the perfectly preserved salt extracting equipment. They can also explore other sections each with their own unique attractions. At the Rudolph mine, visitors will be able to admire the natural salt stalactites that can get up to 12-feet long. In the interior of the cone shaped Terezia mine that lies an astounding 112-meters (367-feet) underground, guests will find a bloom of stalactites along with a magical lake.

Gizela mine (Photo Credit: Salina Turda)

The one area that visitors have no access to is the underground gallery of the Gizela mine. Also known as the Crystal Hall, it has been declared a geological reserve because of the incredible salt crystals and stalactites that lie inside.

Though the Salina Turda Salt Mine is one of the best examples of mine transformations, it is not the only one. In Blaenau Ffestiniog, North Wales, the Blaenau Ffestiniog, North Wales, the Llechwedd slate quarry has been converted into a trampoline paradise. Its massive caverns contain over 10,000 square feet of netting that are suspended 20, 60, and 180 feet above the ground and connected by a network of spiral staircases or slides illuminated by multi-colored lights.

Bonne Terre Mine (Photo Credit: visitmo.com)

Closer to home in Missouri, the Bonne Terre Mine boasts the seventeen-mile-long 'Billion Gallon Lake.' Visitors can take walking tours around what is believed to be the world's largest freshwater dive resort, rent boats to traverse through the various passages or even scuba dive in the pristine waters.

Those looking for a more traditional mining experience can head to the Consolidated Gold Mine in Dahlonega, Georgia. Here they will get an opportunity to learn how the ancient miners lived and also experience their day firsthand by panning for gold or mining for gems. Who knew there is so much entertainment hidden underground?

Resources:salinaturda.com, businessinsider.com,roadtrippers.com