Entering a cave is like going into the past, because it’s usually packed with millennia-old geological formations that have never seen the light of the modern world or heard of the Beatles. Meet a rock that’s been living under a rock with this Groupon to Cascade Caverns in Boerne. Choose between the following options:

• For $11, you get a one-hour cavern tour for two (up to a $22 value).
• For $22, you get a one-hour cavern tour for four (up to a $44 value).<p>

Named a Best Bargain Family Adventure by Southern Living magazine, Cascade Caverns encircles visitors in 64-degree corridors where they can see and feel millions of years of terrestrial history. The old and wizened cave was the first of the six major Texas cave attractions to be discovered, and it is the only one with an interior waterfall, which, at more than 90 feet tall, has inspired awe in throngs of visitors over the years and slowly driven up Batman’s rent. Visitors witness millions of water droplets reflecting brilliantly on the Diamond Ceiling and watch slender stalactite and stalagmite formations slowly work toward their dreams of becoming Corinthian columns.

While moving from corridor to corridor, spelunkers may spot such unusual animals as cliff and leopard frogs, eastern pipistrelle bats, and Cascade Caverns salamanders. Tour-goers can bring a picnic lunch to enjoy before or after their descents, during which time they can also navigate the nature trails that traverse the 105-acre park surrounding the cave. The tour company recommends wearing comfortable walking shoes or hiking stilts and encourages photography.

Though Cascade Caverns sometimes features a discounted price online, this Groupon still offers the best deal available.