Visit the Natural Bridge Caverns – San Antonio, Texas


In early February 2016, we planned a day trip to visit the Natural Bridge Caverns, located between San Antonio and New Braunfels, Texas.  It wasn’t a terribly long ride as it was only about an hour away from where we were parked.  We decided a weekday was best to avoid weekend crowds.  Or, so we thought…

…the day we went happened to be a field trip day of 200 middle schoolers! However, we lucked out, we weren’t anywhere near them.

Its been quite a long time since we’ve visited any caverns. The last time was when we took our son to The Lost Sea in Sweetwater, Tennessee when he was 10 years old.  So, imagine our excitement to go underground to witness the magical wonders of what lurks beneath us twenty years later.

The Natural Bridge Caverns are the largest known commercial caverns in the U.S. state of Texas.The name was derived from the 60 ft natural limestone slab bridge that spans the amphitheater setting of the cavern’s entrance.

A little bit about Natural Bridge Caverns:

The Natural Bridge Caverns are the largest known commercial caverns in the U.S. state of Texas. The name was derived from the sixty foot 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 Natural Bridge Caverns are located near San Antonio, Texas in the Hill Country Region 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 about 70° Fahrenheit year-round and the humidity rate is a constant 99%. The deepest part of the public tour is 180 feet below the surface, although undeveloped areas of the cavern reach depths of 230 feet.


The caverns are still very active and considered living. Due to the porosity of the limestone, rainwater travels downwards through the layers of rock, where it dissolves out calcite, a weak mineral that makes up all of the speleothems at 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 few caverns.



Being with a small group allowed us to appreciate the quiet and true beauty of the cavern.  Our guide led us down into the Cavern after a little history lesson and to see the Natural Bridge that hovers over the entrance.  But first, Bill had to unlock and open the gate at the Cavern entrance tunnel.

When we first entered, we noticed their rules (below photo) to remind those who may want to alter, remove or vandalize the grounds (or under it).


Some geology education here to describe what you see in our photos:

A speleothem, commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone solutional caves.

Over time the accumulation of these precipitates forms stalagmitesstalactites, and flowstones, which compose the major categories of speleothems.

Speleothems take various forms, depending on whether the water drips, seeps, condenses, flows, or ponds. Many speleothems are named for their resemblance to man-made or natural objects. Types of speleothems include:


  • Dripstone is calcium carbonate in the form of stalactites or stalagmites
    • Stalactites are pointed pendants hanging from the cave ceiling, from which they grow
      • Soda straws are very thin but long stalactites having an elongated cylindrical shape rather than the usual more conical shape of stalactites
      • Helictites are stalactites that have a central canal with twig-like or spiral projections that appear to defy gravity
        • Include forms known as ribbon helictites, saws, rods, butterflies, hands, curly-fries, and clumps of worms.
      • Chandeliers are complex clusters of ceiling decorations
    • Stalagmites are the “ground-up” counterparts of stalactites, often blunt mounds
      • Broomstick stalagmites are very tall and spindly
      • Totem pole stalagmites are also tall and shaped like their namesakes
      • Fried egg stalagmites are small, typically wider than they are tall
    • Columns result when stalactites and stalagmites meet or when stalactites reach the floor of the cave
  • Flowstone is sheet like and found on cave floors and walls
    • Draperies or curtains are thin, wavy sheets of calcite hanging downward
      • Bacon is a drapery with variously colored bands within the sheet
    • Rimstone dams or gours, occur at stream ripples and form barriers that may contain water
    • Stone waterfall formations simulate frozen cascades
  • Cave crystals
    • Dogtooth spar are large calcite crystals often found near seasonal pools
    • Frostwork is needle-like growths of calcite or aragonite
    • Moonmilk is white and cheese-like
    • Anthodites are flower-like clusters of aragonite crystals
    • Cryogenic calcite crystals are loose grains of calcite found on the floors of caves, and are formed by segregation of solutes during the freezing of water.
  • Speleogens (technically distinct from speleothems) are formations within caves that are created by the removal of bedrock, rather than as secondary deposits. These include:
    • Pillars
    • Scallops
    • Boneyard
    • Boxwork

See if you can figure out which photos we took (below) match the description of each formation:



This one was actually creepy looking!



This was named ‘Sherwood’s Forest” (no, really, it was!)



The black section you see are reminents of a bat colony aka ‘bat crap’.


The texture of this one was wavy.  Very young Cave Curtains


The only living plant in the cavern
These are called Soda Straws and Broomstick Stalagmites



This is a Column. It looks like the Leaning Tower of Pisa!



This looks like a Jellyfish or  Man O’War, doesn’t it?


A small underground water pooling.  There’s actually tiny organisms in there!


These are called ‘Chandeliers’





We totally enjoyed our 45-minute tour underground.  We learned so much and it gave us an idea of what may lurk under where we walked.

Pretty cool, huh?  Actually it was! Because we were in a cave!

Other things to do…

There were other things to do at Natural Bridge Caverns (ie. wildlife park, ziplines, tower climbing, rock mining, etc. for extra costs but we chose just to do the Cavern.  Its a bit pricey (20 George’s each) but being a commercial venue, what do you expect?  This is a great place to bring the family…especially our RV Homeschoolers!  Something educational and fun!

If you’re looking for other cool things to do in San Antonio or Hill Country…

Bluebonnets in the Spring: Willow City Loop in Hill Country, Texas


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