The karst areas of Wisconsin are located along the eastern and southern border of the state. Silurian and Ordovician dolomites cover large areas in the southern corner of the State. Several show caves are located here. But spacious caverns are rather rare and the speleothems are not comparable to those of other states. The interesting features of those caves are their sediments and solutional features like the profiles of the passages.
A rather small area of Ordovician Prairie du Chien dolomite is in the western corner of the state. Here is another show cave of the state located, Crystal Cave.
The central part of the state is Cambrian sandstone and in the north are even older Precambrian igneous and metamorphic rocks showing no caves at all.