The cave is 47 degrees year-round ... in 1920 and consists of a 21-mile trail system for hikers as well as dolomite limestone cliffs for climbing, according to the Iowa DNR.

Caves in dolomite or limestone are common enough, but a sandstone cave is less common. What happened here is that the dolomite below was more soluble and slowly dissolved away, leaving a cavity ...

This is a dolomite cave system that started forming ... It has over 700 hominid specimens dating back 3.67 million years. The limestone caves, which formed many millions of years ago, preserved ...