Cool off underground: These are the best caves in the US to explore this summer

When the summer sun is blazing, there’s no better way to cool off than by heading underground. Caves offer a naturally air-conditioned escape, along with a chance to explore some of the Earth’s most fascinating geological formations, from delicate stalactites to sparkling crystals.These subterranean wonders offer both a science lesson and an adventure. Whether your vibe is a family-friendly walk or a wild caving crawl, these caves and caverns open the door to a mysterious world shaped over millions of years.

1. Caverns National Park

Carlsbad, New MexicoCarlsbad Caverns National Park is home to more than 119 known caves, celebrated for its immense chambers and striking limestone formations. The star of the show is the Big Room, an underground expanse nearly 4,000 feet long, which can be explored via a self-guided trail. Stop in the visitor center for hands-on exhibits and a 16-minute park film, “Hidden World.” Ranger-led tours are currently on pause, but a $5 audio guide is available. From April through October, catch the nightly flight of over 200,000 Brazilian free-tailed bats. To enter Carlsbad Caverns, you'll need a timed-entry ticket, which you can reserve in advance at Recreation.gov.

2. Mammoth Cave National Park

Mammoth Cave, KentuckyAmid Kentucky’s rolling hills, Mammoth Cave National Park is home to the world’s longest known cave system, with more than 400 miles of mapped underground passages. Visitors can join ranger-led tours, from easy, family-friendly walks to wild cave adventures that involve navigating tight spaces with hard hats and headlamps. The Historic Tour showcases dramatic cave formations with curious names such as Bottomless Pit and Tall Man’s Misery, while the Domes and Dripstones Tour explores the unforgettable Frozen Niagara section. Once described by a 19th-century guide as a “grand, gloomy and peculiar place,” this subterranean wonder is anything but ordinary.

3. Lava Beds National Monument

Tulelake, CaliforniaFormed by half a million years of volcanic activity, Lava Beds National Monument contains the highest concentration of lava tube caves in the U.S. — more than 800 in all. These other-worldly tunnels were created when molten lava flowed beneath hardened surfaces, leaving behind winding, hollow tunnels. There are no ranger-led tours, but you can explore on your own — from the beginner-friendly Mushpot Cave (the only one with lighting) to the more technical Catacombs Cave. Pick up a free permit at the visitor center, where you can also borrow a flashlight and purchase a helmet for safely exploring the world below the earth’s surface.

4. Jewel Cave National Monument

Custer, South DakotaHidden beneath South Dakota’s Black Hills, Jewel Cave is one of the world’s longest caves, with more than 220 miles of mapped passages. It gets its name from the sparkling calcite crystals that that coat chamber walls. Visitors can choose from four ranger-led tours, including the Scenic Tour, which is a great introduction to dramatic chambers and curious formations like cave bacon and cave popcorn. For the adventurous, the Wild Caving Tour offers belly crawls and tight squeezes, requiring hard hats and headlamps. Reservations are strongly recommended and can be made in advance at Recreation.gov.

5. Great Basin National Park

Ely, NevadaLehman Caves, located in Great Basin National Park, is Nevada’s longest cave system, filled with stunning formations. Explore stalactites, stalagmites, and rare cave shields on the ranger-led Parachute Shield Tour, which covers iconic chambers like the Lodge Room, Inscription Room, and Grand Palace, home to the famous Parachute Shield. The caves have been open to the public since 1885, after being discovered by prospector and rancher Absalom Lehman. Tours are available year-round, but book early on Recreation.gov since tickets often sell out.

6. Sequoia & King Canyon National Parks

Three Rivers, CaliforniaCrystal Cave in Sequoia National Park is a marble cavern beneath towering trees, accessible only via naturalist-led tours offered spring through fall by the Sequoia Parks Conservancy. A steep half-mile path leads to the cave entrance, where a loop trail reveals stunning formations and underground beauty. Sequoia and Kings Canyon National Parks are home to at least 275 caves, including some of California’s longest caves. These caves preserve rare minerals and fossils. Reserve your tour in advance as slots fill up quickly, especially in peak summer season.

7. Oregon Caves National Monument & Preserve

Cave Junction, OregonLocated in Oregon’s Siskiyou Mountains, Oregon Caves National Monument and Preserve is home to one of the few marble cave systems in the U.S. Known as the “Marble Halls of Oregon,” the caves were shaped over millions of years by acidic water carving through marble and limestone. Inside, explore stalactites, stalagmites, flowstones, and helictites. Seasonal guided tours showcase Instagram-worthy formations like the Ghost Room and offer options ranging from easy family walks to adventurous off-trail squeezes through narrow passages. Ranger-led tours offer a captivating look at the cave’s geology, ecology and history.

Practical Tips Before You Go:

Before heading underground, keep these tips in mind.Reserve guide-led cave tours well in advance, especially in summer, when they can sell out.Caves stay cool year-round (typically 40 to 55 degrees), so dress in layers and wear sturdy, closed-toe shoes with good grip.To help prevent the spread of White Nose Syndrome, a fungal disease affecting bats, many caves prohibit gear, clothing, or footwear previously worn in other caves. You may also be asked to walk across disinfectant mats.