This 23 sq km national park protects a system of 42 caverns. The only cave with regular public access is the 41m-deep La Terciopelo, which features incredible speleothems (calcite figures that rise and fall in the cave’s interior). It's quite the underground art museum, and its stalagmites, stalactites and a host of beautiful formations have evocative names such as fried eggs, organ, soda straws, flowers and shark’s teeth. Call the ranger station one day in advance to arrange the four-hour guided tour.
Unlike some caverns in other places, Barra Honda is not developed for wide-scale tourism, which means that it feels less like a carnival attraction and more like a scene from Indiana Jones. So, don your yellow miner’s hat and sturdy boots, and be prepared to get down and dirty. The descent involves ladders and ropes, so you should be reasonably fit; children must be at least 12 years old. A small 'cuevita' is appropriate for children under 12.
Tourists must be accompanied by a guide into the cave, and may hike or spelunk at any time of year, provided that the park rangers have determined it is safe. As always, carry several liters of water and let the rangers know where you are going. Sneakers or, preferably, boots are necessary if you will be caving. You will also need a 4WD vehicle to drive from the ranger station to the parking area near the caves. The last allowable descent into the caves is at 1pm.