Limestone reaches the surface and gets subject to weathering.
Ground water starts with the solution of limestone and forms first caves.
A lower drainage system around the limestone area is necessary for the second stage: the rivers and lakes leave the surface, drainage of the whole area is underground.
This is the "typical" stage of a karst area, which we know well from moderate climate zones.
The limestone caves get bigger and bigger and start to collapse.
Cave systems are marked at the surface by daisy chains of dolines.
Dolines merge and form poljes.
The cave systems are more or less collapsed.
The former poljes grew and grew until they are all connected and again form a net of subaerial valles draining the area.
The former limestone plateau is cut into isolated limestone islands.