Deep below the surface of the Transylvanian countryside lies a vast network of caves. Illuminating the eerie darkness are hundreds of fluorescent lights and strange contraptions, a mixture of new and old technology that seems more suited to Batman's lair than to Dracula's mansion.

Welcome to the Salina Turda Salt Mines, the hollowed out remnants of a mining operation that extends back to the 2nd century. First discovered and mined by the Romans, the salt mines were popular throughout the Middle Ages and into the 20th century, until finally closing in 1932. By that time, the mines had been emptied of 3 billion tons of salt, all of which were excavated by hand without explosives, according to Atlas Obscura.

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In 1992 the mines reopened as a museum, and after an expansive renovation, the mines have become one of the most popular and unusual destinations in Romania. Some visitors come for the mines' purported health value - it's thought that breathing the damp, salt-rich air can be beneficial to those suffering respiratory illnesses like asthma and allergies, reported Time.

Others come to the mines to learn about history and see the abandoned mine shafts, such as the conical Terezia Mine or the expansive Antonin Mine. And if neither history nor health is much of an attraction, there are plenty of recreational activities that can be enjoyed hundreds of feet below ground, from mini golf to boating on an underground lake, says the Salina Turda website.

To experience the salty history of the Salina Turda Mines, check out the hours and cost of admission here.

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