i don't know if it's called a karst field, it's a direct translation. Karst or Kras how we call it (the genuine name) is actually a plateau consisting of limestone. it's a unique habitat with unique species and the whole thing about it is that it doesn't hold water, water made a lot of holes throu the limestone, so you can also find large caves. so from our Karst originates the name karst for all limestone regions in the world -karst regions where you can find karst phenomenas such as sinkholes, stalaktites, uvale and also what i've showed a karst polje (pojle means field in Slovenian and i've looked in the dictonary, when talking about karst, polje is an international term)
I thought spelunker is something like that.