Topography

• Caves form when groundwater, which is acidic, dissolves the limestone.Jupiterimages/Photos.com/Getty Images
  
  Caves, sinkholes, small mountains, hills and springs define karst topography, the type of land in limestone regions. Because limestone dissolves in groundwater, parts of the rock eventually become caves. Small mountains form in a similar way, as the slightly acidic water wears away large portions of rock over time. When a surface collapses into an empty space below ground and creates a depression or an actual hole -- called a sinkhole -- it often becomes an important part of the area's natural drainage system.
  
  

Fossils

• Limestone is most commonly composed of marine animal shells.Jupiterimages/Photos.com/Getty Images
  
  Fossil seekers scour caves and sort through rocks in limestone regions to find fossils that range widely in size and origin. Brian Keith, senior scientist at the Indiana Geological Survey at Indiana University, explains that the majority of limestone was formed from whole or broken fossil shells, which had been pulled out of the sea by marine organisms. Limestone fossils also can contain plant and animal debris dating back hundreds of millions of years.
  
  

Quarries

• Quarries mine limestone for many commercial uses.Jupiterimages/Photos.com/Getty Images
  
  According to the Indiana Limestone Institute of America, limestone was first quarried in 1827 in a part of Indiana known as the Limestone Belt, measuring about 30 miles long and 2 miles wide. Although countless institutional buildings are made of the stone -- including the Empire State Building and the Pentagon -- private limestone homes are popular in limestone regions. Jim Owens, technical director/project manager at the institute, says many were built after World War II when the limestone industry was a little slow. Today, limestone is quarried for restoration projects, in addition to the construction of new buildings and roads.
  
  

Warnings

• Inquire about the source of drinking water when visiting limestone regions.Jupiterimages/Comstock/Getty Images
  
  Sinkholes can appear suddenly, so it's wise to use caution when camping or hiking in limestone regions. It's also important to know the source of drinking water in a limestone region because well water and springs can be polluted by sinkholes plugged by trash or affected by chemicals, according to the Cave Conservancy of the Virginias. Visitors to limestone regions also can expect hard water, which can be difficult to clean with and leaves deposits in pipes.