The salt mine, which dates as far back as the 17th century, was used for everything from a cheese storage center to a bomb shelter in WWII after excavations stopped in 1932. Today, it has been transformed into an incredible sci-fi theme park. Located in Ciuj County, Salina Turda has been called one of the coolest underground places in the world. When you visit, you’ll head down about 120 meters (400 feet) before reaching the submerged wonderland. Once inside, you’ll find an amphitheater, a bowling alley, an underground lake with prow boats, and even a Ferris wheel.