New Mexico’s Carlsbad Caverns National Park cave system is of the most magnificent and oldest in the world. It was created long ago as sulfuric acid ate away at the limestone of the Guadalupe Mountains and as rainwater deposited minerals on the caves’ floors and ceilings, slowly building rock formations such as stalactites and stalagmites.
The system is also enormous, with 117 known caves and a voluminous limestone chamber called the “Big Room,” which, at 4,000 feet long, 625 feet wide, and 255 feet high at its highest point, is the third-largest chamber in North America and the seventh-largest in the world. Over the years explorers have mapped 30 miles of passageways, yet the tangled network of underground tunnels has never been fully explored.
Whatever the true extent of the caves, they’re definitely worth a visit, and especially in the summer, when their year-round 56-degree temperatures are a perfect respite from the blazing sun.