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Caves & Caverns

Rock formations inside of the Lehman Caves in Great Basin National Park, Nevada

Some of the most remarkable landscapes in the National Park System are hidden beneath the surface. Caves can contain immense chambers, narrow passageways, underground rivers, delicate mineral formations, unusual wildlife, archaeological evidence, and geological records stretching back millions of years.

The Caves & Caverns hub is the starting point for exploring caves protected within U.S. national parks and other National Park Service sites. From the enormous underground network of Mammoth Cave to the sparkling calcite of Jewel Cave, the famous Big Room at Carlsbad Caverns, the boxwork of Wind Cave, and the talus caves of Pinnacles, these protected underground landscapes reveal an entirely different side of America’s national parks.

Use this guide to explore individual caves, learn how they form, understand the formations and animals found underground, and prepare for a safe and responsible cave visit.

🕳️ Explore Caves in the National Park System

Caves occur in many different kinds of rock and form through several geological processes. Some develop as slightly acidic groundwater slowly dissolves limestone. Others are associated with volcanic activity, coastal erosion, or piles of fallen rock that create passages between enormous boulders.

That means no two national park caves are quite alike. Mammoth Cave is famous for its extraordinary network of passages. Carlsbad Caverns contains enormous rooms and richly decorated formations. Wind Cave is renowned for boxwork, while the caves at Pinnacles formed among fallen volcanic rocks rather than through the dissolution of limestone.

The word cavern is often used for a particularly large or impressive cave or cave chamber, but there is no simple distinction visitors need to memorize. What matters more is understanding how each underground environment developed and why it requires protection.

🦇 Carlsbad Caverns National Park

New Mexico’s Carlsbad Caverns National Park is one of America’s premier underground destinations. Beneath the Chihuahuan Desert lies a complex of more than a hundred known caves, including Carlsbad Cavern itself.

The park’s best-known underground feature is the Big Room, an immense natural chamber filled with stalactites, stalagmites, columns, draperies, flowstone, and other formations. Visitors can explore parts of Carlsbad Cavern along established routes, while more remote caves and passages remain protected for research, conservation, or specialized exploration.

Our guide to the different caves of Carlsbad Caverns looks beyond the best-known chamber to explore more of the park’s subterranean landscape. You can also start with our comprehensive guide to Carlsbad Caverns National Park or explore the must-see attractions at Carlsbad Caverns.

One of the most fascinating things about Carlsbad is that its caves did not develop exactly like many classic limestone cave systems. Sulfuric acid played an important role in dissolving the limestone and enlarging underground chambers, helping produce the remarkable cave landscape visitors see today.

Above ground, the contrast could hardly be greater. Desert mountains, cactus, canyons, birds, reptiles, mammals, and seasonal wildflowers surround an enormous hidden world beneath the surface.

🌎 Mammoth Cave National Park

Kentucky’s Mammoth Cave National Park protects the longest known cave system in the world, with hundreds of miles of surveyed passages and continued exploration adding to our understanding of the underground network.

Explore our Mammoth Cave National Park collection or begin with The Rich History of Mammoth Cave National Park.

Mammoth Cave developed largely within layers of limestone beneath sandstone and other rocks that helped protect parts of the cave from erosion. Water moving through cracks and underground drainage routes gradually dissolved the limestone, creating passages on multiple levels.

Despite the name, Mammoth Cave is not famous because every room is enormous. Its real scale comes from the incredible length and complexity of the entire system. Some passages are broad and imposing, while others are narrow, winding, or relatively undecorated compared with caves known for dense displays of stalactites and stalagmites.

Human history is also unusually important here. People have entered portions of Mammoth Cave for thousands of years. In later periods, the cave became associated with mining, tourism, scientific research, exploration, and the complicated histories of the people who worked as guides and helped reveal the cave to the wider world.

Today, cave tours provide visitors with several ways to experience the underground landscape while leaving the vast majority of the system protected from ordinary visitor traffic.

🌬️ Wind Cave National Park

South Dakota’s Wind Cave National Park protects two dramatically different worlds. Above ground lies prairie and ponderosa pine country inhabited by bison, elk, prairie dogs, pronghorn, and other wildlife. Beneath it is one of the world’s most extensive and complex known cave systems.

Wind Cave takes its name from the movement of air through its small natural entrance. Differences between atmospheric pressure inside and outside the enormous underground system can cause noticeable air movement, creating the impression that the cave is breathing.

Its signature geological feature is boxwork. These thin intersecting blades of calcite project from cave walls and ceilings in honeycomb-like patterns. Boxwork occurs elsewhere, but Wind Cave contains an extraordinary concentration of it and is one of the best places in the world to see the formation.

Wind Cave also has deep significance beyond geology. The cave and surrounding Black Hills are culturally important to Indigenous peoples, and Lakota traditions connect the area with emergence stories and the origins of the people and buffalo.

Visitors can explore portions of the underground system on ranger-guided tours, while the surface provides a completely different national park experience. Our Wildlife of Wind Cave National Park guide explores that aboveground ecosystem in greater detail.

💎 Jewel Cave National Monument

Jewel Cave National Monument is not one of the 63 sites carrying the formal National Park designation, but it is an important National Park Service site and absolutely belongs in a guide to protected caves.

Located in South Dakota’s Black Hills, not far from Wind Cave, Jewel Cave contains more than 220 miles of mapped passages, making it one of the longest known cave systems on Earth. Exploration continues, and scientists believe substantial portions of the system remain undiscovered.

The cave takes its name from calcite crystals that coat many surfaces and glitter when illuminated. Visitors may also encounter stalactites, stalagmites, flowstone, draperies, gypsum formations, and unusual features such as hydromagnesite balloons.

Like Wind Cave, Jewel Cave responds to atmospheric pressure changes with substantial airflow. Measuring this movement has helped researchers investigate the possible scale of the underground system beyond its currently mapped passages.

Jewel Cave also demonstrates why mapping a cave is far more complicated than simply walking through it. Modern explorers survey newly discovered passages carefully so that each route becomes part of an increasingly detailed three-dimensional understanding of the system.

🏔️ Lehman Caves in Great Basin National Park

Eastern Nevada may appear dry and open on the surface, but Lehman Caves in Great Basin National Park reveal an elaborate underground landscape hidden beneath the mountains.

Lehman Caves is the best-known cave within Great Basin National Park, although the park contains dozens of known caves and extensive areas of cave-forming karst terrain.

Visitors to Lehman Caves can see stalactites, stalagmites, columns, flowstone, draperies, and distinctive shield formations. Guided tours provide controlled access while helping protect the cave’s fragile geology and wildlife.

The cave is only one part of the remarkable range of environments within Great Basin. Visitors can move from underground passages to high mountains, ancient bristlecone pines, alpine terrain, and some of the darkest night skies in the country.

That contrast is one of the most compelling things about cave parks. What appears on the surface is often only half the story.

🪨 Balconies Cave in Pinnacles National Park

Not every cave forms because water dissolved limestone.

Balconies Cave in Pinnacles National Park is a talus cave, created when enormous rocks fell into a narrow canyon and became wedged together. Open spaces between those boulders formed dark passages that hikers can travel through when conditions and park regulations allow.

This produces a completely different cave experience from Carlsbad Caverns or Mammoth Cave. Rather than walking through rooms carved from continuous bedrock, visitors move underneath and between massive rocks that have accumulated within the canyon.

Talus caves can change. Rockfalls, storms, flooding, and other natural processes can alter entrances and passage conditions, and closures may sometimes be necessary for visitor safety or wildlife protection.

Pinnacles is also important habitat for bats, giving the caves both recreational and ecological significance.

💧 How Do Caves Form?

The familiar image of a cave being hollowed out by an underground river is only part of the story.

Many caves form in karst landscapes, where soluble rocks such as limestone are gradually dissolved by water. Rainwater absorbs carbon dioxide from the atmosphere and soil, forming a weak carbonic acid. As this water moves through cracks in limestone, it slowly dissolves the rock and enlarges openings.

Over immense spans of time, tiny fractures can become passages, chambers, vertical shafts, and underground drainage systems.

Mammoth Cave is a classic example of a large limestone cave system shaped by water and regional drainage. Other cave systems have different histories. At Carlsbad Caverns, sulfuric acid contributed significantly to cave development. Pinnacles contains talus caves created by fallen rocks rather than chemical dissolution.

National parks also protect lava tubes, sea caves, ice-related caves, sandstone caves, and other underground or cave-like environments.

Understanding how a cave formed helps explain everything from its shape and mineral deposits to the water, wildlife, and hazards found inside.

✨ Stalactites, Stalagmites & Other Cave Formations

Once a cave exists, mineral-rich water can create the formations collectively known as speleothems.

A stalactite forms downward from a ceiling as minerals are deposited from dripping water. A stalagmite develops upward from the floor beneath repeated drips. If the two eventually join, they can form a column.

But caves contain far more than these familiar formations. Visitors may encounter:

  • Flowstone, where mineral deposits spread across walls or floors.
  • Draperies, thin sheets of calcite formed along sloping ceilings.
  • Soda straws, delicate hollow tubes that may eventually develop into larger stalactites.
  • Cave popcorn, clusters of small mineral knobs.
  • Helictites, formations that grow in twisting or seemingly gravity-defying directions.
  • Boxwork, thin intersecting mineral blades especially famous at Wind Cave.
  • Cave shields, unusual disk-like formations found prominently in Lehman Caves.
  • Calcite spar, crystals that contribute to the sparkling appearance of Jewel Cave.

These formations can take extremely long periods to develop and are easily damaged. A formation broken in seconds may represent centuries or millennia of growth.

That is why touching cave formations is prohibited or strongly discouraged in developed cave systems.

🦇 Bats & Cave Wildlife

Caves may look empty at first, but underground ecosystems can contain highly specialized animals.

Bats are the best-known cave residents. Different species may use caves for hibernation, maternity colonies, temporary shelter, or seasonal roosting. Some travel significant distances between feeding areas and roosts.

Other cave organisms can include insects, spiders, crustaceans, salamanders, snails, microbes, and animals adapted to life in permanent darkness.

Species that spend their entire lives underground may develop distinctive adaptations such as reduced eyesight, little pigmentation, enhanced sensory structures, or extremely slow metabolisms.

Caves can also preserve evidence of animals that lived in the surrounding landscape long ago. Bones, fossils, footprints, pollen, and other materials may survive underground under conditions very different from those at the surface.

For more information about animals throughout the parks, explore our Wildlife & Plants hub.

🧬 White-Nose Syndrome & Bat Conservation

One reason cave access is carefully managed is the threat of white-nose syndrome, a serious disease affecting hibernating bats in North America.

The disease is associated with a cold-loving fungus that can grow on bats during hibernation. It has caused severe population declines in numerous bat species.

Visitors can help reduce the risk of spreading harmful organisms by following park decontamination rules. Some caves restrict clothing, footwear, or equipment that has previously been used in another cave. Requirements vary, so always read current park instructions before arriving.

Never ignore these rules because an item appears clean. Fungal spores and other contaminants may not be visible.

Protecting caves means protecting the animals that rely on them as well as the rock formations visitors come to see.

🔦 Visiting a National Park Cave

Cave visits require a different kind of planning from an ordinary national park hike. Underground temperatures may remain cool throughout the year even when surface temperatures are extremely hot. Stairs, steep walkways, low ceilings, darkness, damp surfaces, and narrow passages can also make cave tours more physically demanding than expected.

Some developed caves can be visited on established self-guided routes, while others are accessible only with a ranger. Tour choices may range from relatively short walks to strenuous adventures involving many stairs, crawling, climbing, helmets, and specialized equipment.

Before your visit, check:

  • Whether reservations or timed-entry tickets are required
  • Which cave tours are operating
  • Tour length and physical difficulty
  • Age or height restrictions
  • Accessibility
  • Required footwear or clothing
  • Photography restrictions
  • White-nose syndrome decontamination rules
  • Current cave or wildlife closures

Popular cave tours can fill well in advance, particularly during summer and holiday periods.

⚠️ Cave Safety

Developed cave tours are designed to make underground environments accessible, but visitors still need to take cave safety seriously.

Wear footwear suitable for stairs and potentially damp surfaces. Bring an appropriate layer for cool underground temperatures. Follow the ranger’s instructions and remain on established routes.

Never climb across railings, enter closed passages, wander away from a group, or attempt to explore an undeveloped cave without authorization and the appropriate training.

Wild caves introduce hazards that ordinary park visitors may not encounter elsewhere. Tight passages, unstable rock, vertical drops, deep water, flooding, poor communication, complete darkness, navigation difficulties, and complicated rescues can turn a small mistake into a serious emergency.

Entering a cave should never be treated like simply hiking underground.

🌧️ Caves, Water & Flash Floods

A cave that appears dry can still be part of an active drainage system.

Rain falling miles away may move through underground channels or narrow canyons, and water levels can rise rapidly in certain caves. Talus caves such as those at Pinnacles may also be affected by storms and flooding.

Never enter a cave or narrow canyon when the managing park has closed it because of weather or flood risk. Do not assume clear skies directly overhead mean conditions are safe.

Water is one of the forces responsible for creating and reshaping many caves, and it remains an active part of those systems today.

🧭 Cave Exploration & Mapping

Even some of America’s best-known caves remain incompletely explored.

Professional researchers, park staff, and experienced volunteer cavers continue to discover and survey new passages in cave systems such as Jewel Cave and Wind Cave. Exploration involves far more than finding an opening and seeing where it goes. Teams carefully measure distances, directions, elevation changes, geological features, water, airflow, and other characteristics.

The resulting maps help scientists understand how cave passages relate to the landscape above ground. They can also reveal relationships between groundwater, geology, ecosystems, and areas vulnerable to pollution or development.

Because underground systems do not respect property lines, understanding a cave may require looking far beyond the entrance visible at the surface.

🧪 Caves as Natural Laboratories

Caves provide scientists with unusual opportunities to study geology, hydrology, biology, archaeology, paleontology, mineralogy, climate history, and microbiology.

Mineral deposits can preserve evidence of changing environmental conditions. Sediments may contain fossils or artifacts. Underground water can reveal connections between rainfall and aquifers. Microorganisms living without sunlight can provide insight into life in extreme environments.

These scientific values are one reason many caves have areas closed to ordinary visitors. The most important part of a protected cave is not necessarily the portion equipped with trails and lights.

A visitor may see only a tiny fraction of an underground system while researchers continue studying passages extending miles beyond the public route.

♻️ Protecting Fragile Cave Environments

Caves can be remarkably resilient geological features yet surprisingly fragile visitor environments.

Breaking a formation, leaving trash, touching sensitive surfaces, disturbing bats, introducing microorganisms, writing on cave walls, or wandering into closed passages can create damage that lasts for generations.

Stay on designated routes and platforms. Never collect formations, rocks, bones, archaeological materials, or wildlife. Avoid touching cave surfaces unless a ranger specifically identifies an area where contact is permitted.

Even lint, skin cells, food crumbs, and other material carried underground by visitors can alter heavily visited cave environments over time.

The principle is simple: look closely, learn as much as you can, and leave the underground landscape unchanged.

🗺️ Featured Cave & Cavern Guides

Start exploring the underground side of the National Park System with these National Park Field Guide articles:

🌎 Discover the World Beneath the Parks

National parks are often defined by what we can see from the surface: mountains rising above valleys, rivers cutting through canyons, forests stretching toward the horizon, or wildlife moving across open grasslands.

Caves remind us that an equally complex landscape can exist beneath our feet.

Some underground systems extend for hundreds of miles. Others occupy a single canyon. Some are filled with elaborate mineral formations, while others are notable for fossils, wildlife, groundwater, archaeology, airflow, or unusual geology.

Exploring these places gives visitors a different perspective on national parks. The landscape no longer ends at the ground beneath your boots. Instead, the surface becomes the roof of another environment—one shaped over immense spans of time and still changing today.

Use the guides above to begin exploring America’s protected caves and caverns, then connect them with the mountains, deserts, forests, wildlife, and trails that surround them.

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📚 Sources & Further Reading