There is a tiny state in Southern Europe where 70 per cent of the population of

Karst Topography is a chemical reaction about the dissolution of layer(s) of soluble bedrock, clearly, carbonate rock like limestone or dolomite. Acidic water erodes the calcium in the bedrock, which is a main constituent of carbonate rocks in creating caverns. First tiny fractures/tunnels form in the rock and yet, with adequate time and dissolution, this acidic erosion can make huge caverns.