Kentucky may be famous for bourbon and horses - the pursuits that made these two parents most happy. But for our kids, the Bluegrass State's biggest appeal was to be found underground, in some of the country's most amazing caves.

There are so many, in fact, that we could not begin to scratch the surface, so to speak, as we made time between our tours of horse farms and bourbon distilleries.

Our kids love caves. Last year, when our daughter, Alice, 7, was in first grade, she studied caves. She has been interested ever since, taking her little brother along for the ride.

We managed visits to two caves, like bookends to our vacation - Cascade Cave in Carter Caves State Resort Park to the east, and Mammoth Cave in Mammoth Cave National Park in the center of the state.

Our small tour group at Cascade Cave saw huge rooms, an underground reflecting pool, and bats, which, even though they were sleeping, gave our son, Arthur, 5, the creeps. Alice's favorite rock formations were in the shapes of popcorn and the Great Wall of China. Arthur loved the dragon formation - a stone form that dangled from the ceiling like the open mouth of a roaring beast. He was not so crazy about the moment when our tour guide, Kenny McCoy, turned out the lights to give us a sense of total darkness.

"This is what a cave looks like in its natural state," said McCoy, who has been giving tours of this cave for more than 35 years. "As you can see, they all look the same."

On the other end of the spelunking spectrum is Mammoth Cave, the longest recorded cave system in the world with more than 360 underground miles explored. It is a cave lover's haven, with options for explorers of all levels. There are short and easy tours, photography tours, tours for rock climbers - even a four-hour tour that includes lunch at an underground cafeteria.

Be sure to plan ahead and make reservations, though, as most of the tours are fully booked. A stay the previous night at the park's comfortable hotel made it easier to get to the tours on time.

The two-hour historic tour, which enters through a massive hole in the ground that American Indians discovered 4,000 years ago, seemed like an obvious choice. But after a frank warning from the park ranger - a sort of anti-pep talk that discouraged anyone with claustrophobia or fear of heights or strenuous climbing from heading in - we chose the self-guided option.

It was flexible and quick (all the better to return to bourbon country). But even that basic tour provided an impressive glimpse of shockingly big, cathedral-like rooms, carved by water from the limestone rock.

"It's like layers and layers, like waves of the ocean, but of rock, and it's upside down," Alice said as she scanned the ceiling. "This is amazing."

It might actually have been worth giving up one of the horse stops or distillery tours for a longer visit. Maybe next time.