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the caverns in Virginia

The Natural Bridge Caverns are the largest commercial caverns in the US state of Texas. The name is derived from the 60 feet (18 m) natural limestone slab bridge that spans the amphitheater setting of the cavern's entrance. The span was left suspended when a sinkhole collapsed below it. The caverns are located near the city of San Antonio, Texas, in the Texas Hill Country next to the Natural Bridge Wildlife Ranch, a drive through wildlife safari park. The caverns feature several unique speleothems and other geological formations. The temperature inside the cave is 21 °C (70 °F) year round and the humidity rate is a constant 99 percent. The deepest part of the public tour is 180 feet (55 m) below the surface, although undeveloped areas of the cavern reach depths of 230 feet (70 m). The caverns are still slowly developing. Due to the porosity of the limestone, rainwater travels downward through the layers of rock, where it dissolves out calcite, a weak mineral that makes up all the speleothems at the Natural Bridge Caverns. After exiting the limestone, water enters the caverns where it flows and drips constantly throughout, causing the formations to retain a waxy luster that can be seen in a few caverns.

The caverns were discovered on March 27, 1960, by students Orion Knox Jr., Preston Knodell Jr., Al Brandt, and Joe Cantu from St. Mary's University in nearby San Antonio. On their fourth trip into the caverns, the men discovered/explored just over of passage. Subsequent explorations revealed 2 mile (3 km) associated with what became known as the "North Cavern". After discovery, Knox assisted the landowners in obtaining information and suggestions for development. Clara Wuest Knox dropped out of school to assist. He also approached Jack Burch, who had just finished work on developing the Caverns of Sonora near Sonora, Texas. Burch agreed to help and development began early in 1963. Wuest remarried Harry Heidemann, a retired Texas Highway Patrolman, in the early 1960s. Together, they started work on developing the cavern. The full time development crew included Wuest (now Wuest Heidemann), Heidemann, Burch, Knox, and Reggie Wuest (Wuest Heidemann's son). The cavern has been opened ever since and is still owned and operated by family members. The Natural Bridge Caverns became a registered US National Natural Landmark in 1971. During excavation of the entrance trail, a human tooth, arrowheads, and spearheads dating from 5000 BCE were found. Also, just inside the entrance, a jawbone and femur from an extinct species of black bear were discovered. This leads many to believe that the uppermost areas of the cavern were used as a shelter by early peoples and animals at some point. An archeological dig was recently done under the natural bridge. Archeologists recovered arrowheads and other tools which further indicate the presence of early peoples at some point in history.

In 1967, speculation on a southern extent to the North Cavern was confirmed when test drilling indicated the presence of a large void approximately 90 feet (27 m) beneath the surface. A camera was sent down the narrow shaft and photographs revealed a large chamber filled with formations. This original shaft was reamed out to and three men were lowered into the ground. They discovered a large breakdown chamber and numerous formations. The first three men to enter this room were Jack Burch, Reggie Wuest, and Myles Kuykendall. By combining the first two letters of each man's first name, they arrived at JAREMY, and thus this newly discovered room was called the Jaremy Room. Further investigation near the bottom of the Jaremy Room revealed a strong likelihood that another passage existed beyond a pile of rocks and boulders. In 1968, the drillers were once again brought out to the property and another exploratory shaft was sunk into the ground. During mid 2005, several hundred feet were added to the current surveyed length of the cave. It is believed that as much as another mile (1 mile (2 km)) could be added to the survey by just mapping the known passages which have not yet been surveyed. Additional unexplored leads exist in sections of the Discovery Passages (North Cavern). Since May 8, 2019, a team of cave explorers have discovered over 1600 feet (488 m) of new never before seen passages. As explorers move deeper into the cavern, each expedition takes longer, with the latest taking more than 19 hours to complete.

In 2008, the caverns' owners changed the names for the passages.

Located on the property is the Natural Bridge Caverns Sinkhole Site, an archeological site listed on the National Register of Historic Places. The location of the site is not publicly disclosed in order to preserve artifacts in their context for ongoing research.