One-of-a-Kind Destinations: 11 National Park Curiosities

1. Rocks that slide like ghosts over the desert

For decades, no one knew how the rocks in Death Valley’s Racetrack moved—seemingly like ghosts—across this dry lakebed in a remote northern section of the park; people just saw the long, streaked trails these boulders left behind in the mud as they moved gradually across the flat dirt. In late 2013, scientists released new research, believing they had finally solved the mystery: Winds push these rocks on thin layers of ice, propelling them slowly along the ground. No matter how it happens, the phenomenon is one of the odder spectacles in the park system. Some of these rocks weigh hundreds of pounds, yet they glide through one of the hottest areas of the country in a manner more typical of an arctic climate.

2. The longest arch bridge in the country

When builders completed this 3,030-foot-long steel bridge in 1977, they turned a winding 40-minute mountain drive into a quick and easy trip over the scenic New River. Now, the bridge is one of the most-photographed sites in West Virginia and a historic resource on the National Register of Historic Places. On the third Saturday of every October, park officials host Bridge Day, the biggest festival in West Virginia and one of the largest extreme sporting events in the world. Bridge Day is the one day a year that BASE jumping, rappelling, sky-diving, and other activities are allowed on and around the 876-foot-tall bridge. Visitors can enjoy less-daring pastimes, too, like hiking the gorge and sampling local foods and crafts.

3. Miles of rare, crystal-white dunes

They may look like mounds of snow, but the dunes in this park are made of a rare form of crystallized gypsum. Because gypsum dissolves easily in water, rain would normally wash it away and carry it to the sea. In this part of the Chihuahuan Desert, however, the land forms a basin, trapping the mineral; water evaporates, leaving the gypsum behind, and wind and weather erode it over time into an ocean of glittering sand. The entire dune field is a massive 275 square miles (by comparison, the second-largest gypsum dune field in the world, Cuatro Ciénegas in Mexico, is only 8 square miles). Hiking and sledding over this vast white expanse of powder is a singular, otherworldly experience.

4. More hoodoos than anywhere else on Earth

Anyone who has been to Bryce Canyon knows the beauty of these quirky rock formations, but what is a hoodoo exactly? These columns of stone have alternating layers of hard and soft rock; frost and weather erode the pinnacles into unusual shapes, often forming thin spires with a cap of harder rock on top. This hard cap sometimes appears as a larger “head” on a thin “body,” and may explain why the French call these formations demoiselles coiffées (“ladies with hairdos”). Whatever you call them, you can see more of them at Bryce Canyon than anywhere else on the globe. You can even hike from the rim down into the main amphitheater and walk among them as they tower over you—an experience that can feel like exploring another planet.

5. A gigantic steel symbol of the American spirit

At 630 feet high and 630 feet wide, St. Louis’ iconic Gateway Arch is the tallest arch in the world and the tallest monument in the Western Hemisphere. For those counting at home, that’s 75 feet taller than the Washington Monument and more than twice as high as the Statue of Liberty. This National Historic Landmark was completed in 1965 to commemorate the westward expansion of the United States and Thomas Jefferson’s role in sponsoring the Lewis and Clark Expedition, which departed from the St. Louis area in the early 1800s. The elegant design was also intended to symbolize the American pioneer spirit. For a modest fee, visitors can take a tram ride to the top of the arch or a cruise on the Mississippi River below it for fantastic views of the area.

6. The only place alligators and crocodiles live together

Alligators and crocodiles belong to the same order of reptiles and look remarkably similar, yet these toothy, sun-loving creatures have distinct physical characteristics and largely live in incompatible environments. Crocodiles prefer salty or brackish water; alligators (shown here), on the other hand, like rivers, swamps, and other freshwater environments, and only make their homes in a few regions of the United States and China. Because of these irreconcilable differences, there is only one place with habitat diverse enough to host both species: South Florida, most notably the Everglades. Perhaps this is not a huge surprise, since this region is known for its many plants and animals, including hundreds of bird species, endangered panthers and manatees, and 39 types of native orchids.

7. The largest sand dunes in North America

How can something that is constantly shifting stand up to 750 feet tall? Geologists are still studying the mysteries of the sands that make up the massive dunes at this southwestern park, though the key to their extraordinary height seems to lie in the combination of strong opposing winds and the presence of rivers and creeks, which capture drifting sands and redeposit them back on the dunes. Some of these remarkable hills are formations known as star dunes—including the very tallest, named, simply, Star Dune. Complex wind patterns form these multi-pronged shapes, which look a bit like starfish from above. The grains blow in different directions, creating the dunes’ angled “arms.”

8. An “old man” floating upright for more than a century

Oregon’s famously clear, jewel-blue lake is the deepest in the country and the centerpiece of one of the most popular parks in the National Park System. But what many visitors may not know is that this spectacular caldera has had something unexpected bobbing in its waters for nearly 120 years—a 30-foot hemlock log, fondly dubbed the “Old Man of the Lake.” First spotted in 1896, the Old Man has somehow managed to stay perfectly balanced for decades, long after other logs have eroded and sunk. “He” has also become something of a local celebrity in the process, as park visitors find themselves alternately calmed and spooked by his presence. See National Parks magazine for more on this unusual tree.

9. The world’s largest underground labyrinth

It may be difficult to think of caves as spacious and grand, but the caves in this world-famous park are no ordinary subterranean experience. Humans first discovered this complex limestone labyrinth some 4,000 years ago beneath the Green River Valley and the oak and hickory forests of Edmonson County, Kentucky. To this day, explorers have yet to find an end to it, despite mapping more than 400 miles of passageways. It is by far the longest such system in the world, featuring nearly every type of cave formation in its many paths, shafts, and chambers. This site also features the richest known habitat for cave wildlife in the world; 130 different species make their home here—14 of which can’t be found anywhere else.

10. The only museum dedicated exclusively to the history of immigration

Across the harbor from New York’s famous Statue of Liberty, officials at the federal immigration station on Ellis Island processed some 12 million immigrants between 1892 and 1954, making it the busiest station of its time. In the years since, the Park Service has operated a museum in the former facility, sharing the immigrant experience with visitors. The recently expanded offerings feature comprehensive educational exhibits, including historic and modern trends on how people move around the world and information on slavery as a form of forced immigration. The only museum of its kind, the facility allows visitors to immerse themselves in first-hand accounts of people who undertook lengthy journeys and overcame serious hardships to begin a new life in America.

11. Exploded craters of vast blue water

From 17,500 to 100,000 years ago, magma from volcanoes in this remote region of Alaska came into contact with permafrost, resulting in hundreds of powerful and prolonged steam explosions. These explosions, which one scientist describes as a “Pleistocene Pompeii,” created four gigantic craters that subsequently filled with rainwater. The resulting deep blue lakes, called maars, measure up to five miles long and are largest lakes of their kind anywhere in the world. Accessible only by float plane, these dramatic waters are the northernmost examples of maar lakes on the globe.