Laurel Caverns
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Laurel Caverns, formerly known as Dulaney's Cave and Laurel Hill Cave, is the largest cave in Pennsylvania. It sits on the Chestnut Ridge near Uniontown, Pennsylvania, about 50 miles southeast of Pittsburgh.
Laurel Caverns is a privately-owned show cave with an hour-long guided tour. Its difference is that it is not a limestone cave, but rather occurs in sandstone made up of silica grains cemented together with calcium carbonate. The cave formed when the calcium carbonate was dissolved by groundwater allowing the silica to be washed away. This gives the cave rough walls, a sandy floor, and formations not seen in the more common limestone caves. Laurel Caverns was also formed in an area of folded and fractured rock. Because of this, the entire cave is tilted fifteen degrees, resulting in many steep passageways. They tend to follow the fractures in the rock, resulting in a grid of long passageways.
The cave has been known to history since the 18th century, and probably used by the Native Americans long before that. It is home to many bats and stays at a temperature of 12°C (55°F) year round.
The steep slope of some passageways causes an interesting optical illusion known as a gravity hill. The brain is confused and tends to underestimate the slope. A demonstration in which a ball appears to roll uphill illustrates this.
