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Smith Rock State Park, Oregon - Located near the communities of Redmond and Terrebonne, the sheer cliffs of tuff and basalt are ideal for rock climbing of all difficulty levels.

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Titan Missile Museum, Arizona - Delve underground and explore this former secret intercontinental ballistic missile site. (Photo: Flickr/CC BY-NC-ND 2.0)

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Fort Jefferson, Florida - This massive but unfinished coastal fortress is the largest brick masonry structure in the Americas.

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Apostle Islands National Lakeshore Ice Caves, Wisconsin - The sandstone sea caves on the shore of Lake Superior ice up in winter to astonishing effect.

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Fly Geyser, Nevada - This lesser-known geothermal crowd-pleaser is constantly spitting out boiling, mineral-rich water.

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Garden of the Gods, Colorado - Peppered with outstanding rock formations, the park is a favorite for hiking, rock climbing, mountain biking, and horseback riding.

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Tamanawas Falls, Oregon - In winter you'll have to snowshoe the trail leading up to this magnificent waterfall. The summer months provide the perfect picnic opportunities.

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Bodie, California - A boom town in the late 19th century, Bodie today is an eerily silent ghost town.

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Roaring Fork, Tennessee - The stream's area is home to the verdant Roaring Fork Motor Nature Trail and the Roaring Fork Historic District.

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Mendenhall Glacier, Alaska - Here you can see the rich colors of sunlight filtered by the thick ice of the enormous glacier. The Mendenhall Glacier Visitor Center offers interpretive programs throughout the year for children and adults.

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Chiricahua National Monument, Arizona - Marvel at the awesome landscape of extensive hoodoos and balancing rocks.

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Blue Lakes, Colorado - It's as if somebody has poured liquid turquoise into the waters of these beautiful lakes.

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Biosphere 2, Arizona - Take the "Under the Glass" guided tour and learn more about this fascinating Earth system science research facility.

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The Wave, Colorado - This curvaceous sandstone rock formation is situated in the Paria Canyon-Vermilion Cliffs Wilderness.

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Dutch Village, Iowa - The lofty Vermeer Windmill is the largest Dutch windmill in the United States.

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Elephant Rock, Nevada - An "elephant" appears to loom out of the bright red Aztec sandstone outcrops at Valley of Fire State Park that lend the valley its name.

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White Sands National Monument, New Mexico - The fantastic wave-like dunes of gypsum sand have created the world's largest gypsum dune field.

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Byodo-in Buddhist Temple, Hawaii - A replica of a 900-year-old Buddhist temple in Uji, Japan, this serene destination is set against the towering Ko'olau mountains.

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Oak Alley Plantation, Louisiana - The plantation is located on the Mississippi River and distinguished for its double row of southern live oak.

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The Boneyard, Arizona - The Boneyard is a secret aircraft boneyard where retired jets are parked in rows, resembling winged tombstones.

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Paint Mines Interpretive Park, Colorado - The landscape is distinguished with a colorful clay that once provided pigment for American Indian pottery.

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Hanging Lake, Colorado - A scenic beauty spot worth pulling over for as you travel the spectacular Colorado River-carved Glenwood Canyon.

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Ward Charcoal Ovens State Historic Park, Nevada - The unique beehive-shaped ovens were constructed in the latter half of the 19th century for creating charcoal for the smelting of ore.

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Eastern Plains, Colorado - A frigid sunrise illuminates the Colorado Eastern Plains, a very sparsely populated region of the nation.

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Bok Mountain Lake Sanctuary, Florida - The sanctury's 205-ft (62-m) tall Singing Tower with its carillon bells is an often overlooked Florida landmark.

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Whitehall (Henry M. Flagler House), Florida -

Dating back to 1902 is this plush, 75-room Gilded Age mansion, which is open to the public.

(Photo: Flickr/CC BY-NC-ND 2.0)

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Mildred B. Cooper Memorial Chapel, Arkansas -

This extraordinary place of worship is built from steel and glass to create a series of Gothic arches that run the length of the chapel.

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Assateague Island National Seashore, Maryland - This barrier island composed of a constantly shifting ribbon of sand is famed for its wild horses.

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Great Sand Dunes National Park and Preserve, Colorado - The tallest dunes in North America draw outdoor enthusiasts from across the country.

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Plum Island, Massachusetts - Named for the wild beach plum shrubs that grow on its dunes, the barrier island is located off the northeast coast of Massachusetts.

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Arches National Park, Utah - A red-rock wonderland where nature's stonemasons have seemingly honed their craft.

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Multnomah Falls, Oregon - The cascades of Multnomah Falls are among the most dramatic and picturesque natural water features in the country.

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Florida buoy sign, Florida - The famous Key West Buoy sign marks the southernmost point in the continental USA and states the distance to Cuba.

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Cathedral Room, Montana - The vast, lilac-washed "Cathedral Room" is simply dazzling.

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Plaza Blanca, New Mexico - So named because the sandstone cliffs spearing the sky appear almost white in the full afternoon sun.

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Crater Lake National Park, Oregon - With a depth of 1,943 ft (592 m), this is the deepest lake in the country—and one of the most beautiful!

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International Car Forest of the Last Church, Nevada - Beat up and abandoned vehicles, graffiti, and religion combine to create this bizarre jungle of scrap in the middle of the desert. (Photo: Flickr/CC BY-NC-ND 2.0)

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Balanced Rock, Idaho - Resembling a huge Stone Age question mark, the wind-carved rock balances precariously on a pedestal only 3 ft (0.9 m) by 17 in (0.4 m).

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Hawai'i Volcanoes National Park, Hawaii - The park encompasses two active volcanoes, Kīlauea and Mauna Loa. The molten bath time is a stunning sight.

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Wupatki National Monument, Arizona - The area contains many well-preserved American Indian Anasazi and Sinagua ruins at the edge of the Painted Desert.

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Haleakala Volcano, Hawaii - It's worth the steep hike to admire a truly breathtaking landscape.

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Crystal Bridges Museum of American Art, Arkansas - Get caught up with the giant metal spider sculpture, one of the museum's signature pieces.

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Bodie Island Lighthouse, North Carolina - Built in 1872, the landmark lighthouse illuminates the Cape Hatteras National Seashore, on the Outer Banks.

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Turner Falls, Oklahoma - An adventurous and family-friendly annual destination for those in the know.

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Molokini Crater, Hawaii - Hawaii's only island marine sanctuary is also a popular tourist destination for scuba diving and snorkeling.

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Denali National Park and Preserve, Alaska - Dominating a skyline of precipitous granite spires and snow-capped peaks is North America's highest mountain. Denali ascends majestically to 20,310 ft (6,190 m).

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Gillette Castle State Park, Connecticut - The quirky castle was originally a private residence, commissioned and designed by actor William Gillette (1853–1937).

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Pecos National Historic Park, New Mexico - This destination encompasses prehistoric archaeological ruins, 19th-century ranches, a Civil War battlefield, and the Pecos Pueblo, a former American Indian community.

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The Lost Sea, Tennessee - This remarkable body of water is listed by the Guinness Book of World Records as America's largest underground lake.

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Cecret Lake, Utah - The Cecret Lake (sometimes spelled Secret Lake) is a rarely visited alpine lake sunk in Albion Basin.

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Heron Pond Cypress Swamp, Illinois - An environment you'd expect to find in the country's southern states, the Heron Pond Cypress Swamp is a rare northern wonder.

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Rehoboth Beach, Delaware - Delaware's beaches are among the most inviting and pristine found along the eastern seaboard.

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Death Valley National Park, California - Only the truly adventurous (or seriously insane) venture into the hottest, driest, and lowest national park in the country.

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Neon Museum, Nevada - Mull over a collection of glittering signs and billboards that once shone above the city that never sleeps.

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Lunar Crater, Nevada -

Ever wondered how the Apollo astronauts were so adept at walking on the moon? This is where they trained.

(Photo: Flickr/CC BY-NC-ND 2.0)

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Pyramid Lake, Nevada - Pyramid Lake is admired for its tufa rock formations that look more like they belong in Egypt.

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Mammoth Cave National Park, Kentucky - This is the world's longest known cave system, with more than 400 mi (644 km) of tunnels explored. But there's still plenty to discover.

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Eldred Rock Lighthouse, Alaska - Listed on the National Register of Historic Places, the lighthouse epitomizes the wilderness that is Alaska.

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Sleeping Bear Dunes National Lakeshore, Michigan - These sleeping beauties are enormous walls of sand that front Lake Michigan's eastern coastline.

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Barrow, Alaska -

The northernmost city in the United States has been home to the Iñupiat, an indigenous Inuit ethnic group, for more than 1,500 years.

See also: Underexplored places you should definitely visit

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