Cave of the Mounds, a natural limestone cave located near Blue Mounds, Wisconsin, USA, is named for two nearby hills called the Blue Mounds. It is located in the southern slope of the East Hill. The cave's beauty comes from its many varieties of mineral formations called speleothems. The Chicago Academy of Sciences considers the Cave of the Mounds to be "the significant cave of the upper Midwest" because of its beauty, and it is promoted as the "jewel box" of major American caves. In 1988, the United States Department of the Interior and the National Park Service designated the cave as a National Natural Landmark.
Cave of the Mounds is home to many varieties of speleothems. As with most caves, stalactites and stalagmites are common. Formations found inside the cave include:
- Soda straws - Soda straws are formations characterized by thin, hollow tubes made of minerals. They have the potential to form into stalactites if the holes at the bottom of them become plugged.
- Flowstones - Flowstones are created when water travels along a surface and deposits minerals. In limestone caves, flowstones are generally the most common type of formation.
- Curtains - These are formed when water droplets run along the ceiling of the cave and gradually form sheets of minerals.
- Lily pads - Lily pads are created when water droplets fall into a puddle and create a formation on the surface reminiscent of a lily pad.
- Helictites - Helictites are an unusual form of stalactite that grow with bends or angles in them that seem to defy gravity. Their strange growth style is most likely caused by capillary forces acting on the water droplets.
- Oolites - Also called "cave pearls", they are a beautiful but rare speleothem. These are spherical formations made when a droplet falls onto some sand and calcite forms around the sand, much like the way a pearl is formed.
These formations come in many different brilliant colors such as reds, browns, blues, and grays. The reds and browns are caused by the presence of iron oxide in the formation. Similarly, blues and grays are caused by manganese oxide. Some speleothems are even partially luminescent and give off light for a brief period after exposure to another light. Somewhere in the cave, there is a large orthoceras that you can spot
The cave is located 20 miles west of Madison
, off U.S. Highways 18/151 in Blue Mounds, Wisconsin. Since its opening in 1940, the cave has hosted millions of tourists.