WARSAW (AFP) - One of the oldest salt mines in Europe, Poland's Wieliczka, on Tuesday called for photos of salt from across the globe for a contest and show at its underground museum.

"We thought it would be good to learn about the rest of the world's salt and compile a portrait of it," museum spokesman Malgorzata Bogucka told AFP.

She said submissions should focus on how NaCl is made, clarifying that a snapshot of a salt shaker would not make the cut.

The mine in Wieliczka, a southern town 15km from Krakow, dates back to the 13th century, when its salt was discovered.

With galleries spanning some 300km, it has become a major tourist attraction and a Unesco World Heritage site that draws more than a million visitors a year.

Its curiosities include statues of gnomes and historical figures sculpted from salt, underground lakes and a subterranean hotel and sanatorium.

It also boasts an underground chapel carved from salt - including a version of The Last Supper and a chandelier - that holds public mass every Sunday.

The winner of the photo contest will receive US$2,000 (S$2,518) and the best shots will go on display at the mine, 135m underground, starting December.

The show will then hit the road next year, though the venues abroad have yet to be nailed down.

Bogucka said the museum held a EU-wide photo contest in 2011 that drew submissions from around a dozen countries, including France, Denmark, Bulgaria and Ireland.

The mine is still operational today, though it stopped producing salt on a large scale in 1996.