Karst is defined as a terrain with distinctive landforms and drainage arising from greater rock solubility in natural water that is found elsewhere. This definition is part of the first site regarding this topic entitled Karst (1), which is provided by Purdue University instructor Robert Hall. The PowerPoint presentation provides a general introduction to the subject, tells how karst landforms develop, how climate affects them, and describes the different types of caves that can occur. The second site, Karst Topography Teacher's Guide and Paper Model (2), is maintained by the US Geological Survey. Visitors will find a thorough description of what karst landforms are, names and locations of underground karst features, a glossary of karst terminology, and a link to a karst system paper model that students can print and construct on their own. The third page related to karst, which is part of the larger Karst Waters Institute Web site, is called the Top Ten List of Endangered Karst Ecosystems (3). The page includes a world map that shows the locations of these ecosystems and contains descriptions of each including why they're endangered and what should be done to protect them. Next, from the Canadian Cave and Karst Info Sever, comes the Glossary of Karst Related Terms (4) Web site. This comprehensive glossary contains dozens of terms that includes everything from anastomosis to zonation in a well-designed and easy-to-read format. The Karst Pages Web site(5) is maintained by DyeTracing.com. This informative page contains links to eight topics that include an introduction to karst, theories of cavern development, hydrology of aquifers, karst environmental problems, and more. Each contains simple descriptions and several graphics, making it an easy and interesting read. The sixth site provided by the National Park Service is a teachers guide called More Than Skin Deep (6). The activities provided have names that include making your own cave, seepy sandwich (groundwater), clay cave (cave formation), making your own stalactite, and other quality activities and information pages. Winona State University maintains the next site called Karst is an Unusual Landscape With Special Groundwater Quality Issues (7). This well done site contains six topics that include Karst Landscapes of Illinois, Texas Caves and Karst, Description of Missouri Karst, a Simple Animation Showing Formation of a Karst Landscape, Description of Karst in Ohio, and a Description of Karst in Kentucky. Each does a good job of explaining the topic and providing interesting photographs and other graphics that help clarify the subjects. The last site entitled Indiana Geology Visual Dictionary (8) is provided by the Indiana Geological Survey. Visitors will find a Karst Features and Stages of Development Flash file, as well as a whole host of other related terms.