What lies beneath can be cold, damp and compelling. Here's where you can learn about dry and wet caves, the creatures that live in them and the characteristics that create these natural settings.

1. KARTCHNER CAVERNS, BENSON, ARIZONA In 1974, two University of Arizona students and amateur cavers spotted a narrow crack in the bottom of a sinkhole. They followed the moist air and discovered more than 2 miles of unspoiled cave passages. Visit this living or "wet" cave which features a 22-foot-long "soda straw" stalactite, reported to be the second longest in the world.

INFO nwsdy.li/kartchner

2. LURAY CAVERNS, LURAY, VIRGINIA In 1878, a tinsmith and several adventuresome friends were exploring the countryside and found this widely visited cavern system. It is perhaps most well known for its Great Stalacpipe Organ, a lithophone that produces tones similar to musical instruments. Check out several on-site museums, including Toy Junction, which is popular with the junior set.

INFO luraycaverns.com

3. MAMMOTH CAVE NATIONAL PARK, MAMMOTH CAVE, KENTUCKY This park in the hill country of south central Kentucky preserves the world's largest known cave system. Explore 400 miles of vast chambers and complex labyrinths on a variety of tours. If you are not sure spelunking is for you and your family, consider the short, small-group Introduction to Caving tour.

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INFO nps.gov/maca

4. CARLSBAD CAVERNS NATIONAL PARK, CARLSBAD, NEW MEXICO Underneath the magnificent desert landscape of southeastern New Mexico and West Texas are more than 300 known caves. Visitors to the park, two-thirds of which is a designated wilderness area, can inspect more than 100, including some of the largest caves in North America. The 8.2-acre Big Room is partially wheelchair accessible.

INFO nps.gov/cave

5. CASTLEGUARD CAVE, BANFF, ALBERTA This remote underground marvel is known for rare cubic cave pearls and an array of flagged "soda straw" stalactites. Experienced explorers can stay in the cave at one of two underground camping sites within Banff National Park and study the unique plugs of glacial ice pushed into the cave from the sole of a surface ice field.

INFO pc.gc.ca