Almost everyone has at one time or another heard of, or read about, caves. They provide a view into an underground world populated with bats and uncommon creatures such as blind, colorless insects and fish. Natural caverns, large enough to hold entire buildings, may contain beautiful and delicate structures fashioned by nature from water and rock. Humans have been exploring, living in and decorating caves for thousands of years. Today we can examine pictures on cave walls that illustrate the world in which humans Lived 20,000 to 30,000 years ago. As recently as the early nineteenth century, Native Americans and European settlers in Minnesota were using natural and man-made caves along the Mississippi River bluffs in what is now the present-day Twin Cities Metropolitan Area (Alexander, 1980). In the popular writings of Mark Twain, Tom Sawyer and others frequented caves farther south along the Mississippi River. And what would the story of Aladdin have been without the cave used by the forty thieves? Some of our national parks, such as Mammoth Cave in Kentucky, and Carlsbad Caverns in New Mexico, were established to protect large caves and to provide public access to the unique and often fragile underground world. Caves are only one part of a group of landscape features known as karst. Karst landscapes are broad and regional in nature. In addition to caves, karst landscapes include, but are not limited to, underground streams, sinkholes, blind valleys, and springs.