Salt is found in big underground layers where ancient seas dried up millions of years ago. The Romans started mining salt here almost 2,000 years ago, breaking blocks out with picks and dragging them to the surface in baskets. Mining carried on for nearly 2,000 years until the mine finally closed in 1932.
When the miners left, they left behind enormous hollow chambers - some bigger than a cathedral - all carved out of solid salt rock. The walls and ceilings glitter where light catches the salt crystals. For 60 years the mine just sat there, quiet and cold.
In 2010, the mine was reopened as a tourist attraction with a brilliant idea: turn the empty chambers into an underground theme park. There is a Ferris wheel that turns slowly inside one giant chamber. There is a small lake, deep underground, where visitors can hire rowing boats. There is a mini-golf course, table tennis, a bowling alley, even an amphitheatre.
The temperature inside stays the same all year - around 10 to 12°C - so you need a jumper even in summer. Doctors think that breathing in the salty air is good for people with chest problems, so some visitors come just to sit in the chambers and breathe deeply.