The miners carved chapels out of the salt. This is on the first level, around 100m underground IIRC.
The rock is, of course, run with salt.
When water seeps through it the result is rather dramatic looking "cauliflowers"
Some parts could be directly out of a dwarven kingdom in The Lord Of The Rings.
Apparently they even kept horses down here, including stabling them underground, to turn heavy cranks and the like.
Let it rain salt?!
Further content from Tokien, complete with model dwarves.
And a dwarven hall!
Remember, all this is carved out of the rock - 90% salt in most cases - over 100m below ground!
The dwarves also have pools of fully salt saturated brine.
Legend has it some miners once got trapped in an overturned boat in this water and were unable to dive out of it because the salt renders you shockingly buoyant.
The man who led modern Poland essentially into existence.
The mine goes something like eight levels but only three are open to tourists. The deepest one we went into was 130m underground.