The primary attraction of the park is the show cave Carlsbad Cavern. Visitors to the cave can hike in on their own via the natural entrance or take an elevator from the visitor center.
Carlsbad Cavern includes a large limestone chamber, named simply the Big Room, which is almost 4, ft 1, m long, ft m wide, and ft 78 m high at its highest point. The Big Room is the largest chamber in North America and the 32nd largest in the world. In , Carlsbad Caverns was established as a national park and was also recognized as a World Heritage Site in According to The Travel, it is renowned globally for being "one of the most accessible and best-preserved cave complexes in the world".
An estimated million years ago, the area surrounding Carlsbad Caverns National Park served as the coastline for an inland sea. Present in the sea was a plethora of marine life, whose remains formed a reef.
After the Permian Period, most of the water evaporated and the reef was buried by evaporites and other sediments. Tectonic movement occurred during the late Cenozoic , uplifting the reef above ground. Susceptible to erosion, water sculpted the Guadalupe Mountain region into its present-day state.
Carlsbad Caverns National Park is situated in a bed of limestone above groundwater level. During cavern development, it was within the groundwater zone. At a time near the end of the Cenozoic, hydrogen sulfide H 2 S began to seep upwards from the petroleum into the groundwater. The sulfuric acid then continued upward, aggressively dissolving the limestone deposits to form caverns. The presence of gypsum within the cave is a confirmation of the occurrence of this process, as it is a byproduct of the reaction between sulfuric acid and limestone.
