At 3.8 million square miles, the United States is the third largest country in the world. With all that room to roam, it's no surprise that America has some absolutely beautiful national parks. But how much do you know about them, really?




1. A remote Native American tribe lives deep inside the Grand Canyon



As a natural wonder of the world,Grand canyon is one of the most popular tourist attractions in America. But while most travelers only come for a quick visit, there is actually a community that lives full-time at the base of the canyon.Within the Havasupai Indian Reservation. Supai Village has a population of 208and is the most remote settlement in the lower 48. In fact, it's so off the grid that the mail has to be delivered by pack mule.

2. The 750-foot-tall dunes at Great Sand Dunes National Park actually sing




This Colorado national park is home to the tallest sand dunes in North America, soaring about 750 feet in the sky. But the dunes have a special secret: They sing! When there's an avalanche, the sand starts to hum deeply. This sound was the inspiration behind Bing Crosby's 1942 hit "The Singing Sands of Alamosa." If you want to see them for yourself, rent a sandboard or sled to zoom down the sandy slopes!

3. One of the waterfalls at Yosemite National Park looks like Lava


At golden hour in mid- to late-February, Horsetail Fall in,Yosemite Nation Park is transformed. The way the sun's rays hit the cascade, it looks like a fiery lava flow off the side of a cliff. This is also a nod to the park's historic Firefall, which started in 1872 when the owner of the Glacier Point Hotel would throw campfire embers from the summit of Glacier Point every night until the practice ended in 1968


4. The fireflies at Congaree National Park put on a light display every summer



Congaree has the largest old-growth bottomland hardwood forest in the U.S. Even more phenomenal? For a month in early summer, between the end of May and the start of June, thousands of fireflies simultaneously light up each night at exactly the same time for a magical natural show.And for more fairytale views, browse through the 100 Destinations So Magical You Won't Believe They're in the U.S.

5.The hot springs at yellowstone are so acidic,they can dissolve a human body overnight


Yellowstone is the most iconic park in America—and also the world's first national park (established in 1872 by President Ulysses S. Grant). It has the largest number of mammal species, its own Grand Canyon, and half the world's hydrothermal features, including mud pots, geysers, and hot springs. The latter of which are so acidic, they can actually dissolve a human body overnight.

6. There's an underground lunchroom hidden 750 feet below Carlsbad Caverns National Park



This 47,000-acre national park—which was once part of an ancient underwater reef—contains more than 120 caves beneath its surface. Although visitors in the early 20th-century had to be lowered into the caves in a bucket, it is now very easy to access. So simple, in fact, that an underground lunchroom was built in one of the chambers 750 feet below ground.

7. North Cascades National Park was the inspiration behind two iconic Beat Generation novels



For two months, author Jack Kerouac worked at this Washington national park as a Park Service fire spotter and lived in a cabin on Desolation Peak. He later used this experience as material for two novels, including The Dharma Bums.


8. One of President Lincoln's assassinators was imprisoned in the fort at Dry Tortugas National Park





Dry Tortugas National Park spans a series of islands some 70 miles from Key West. Its striking centerpiece, Fort Jefferson, is an unfinished coastal fortress that is the largest brick masonry structure in the Western hemisphere. During the Civil War it served as a prison and had famous inmates such as Samuel Mudd, who was involved in President Abraham Lincoln's assassination.



9. There are more than 3,000 fruit-picking trees in the barren Capitol Reef National Park


There's one fairly unusual activity you can participate in while you're here: fruit picking. The national park in Utah has 3,100 fruit trees, including apple, pear, peach, and cherry trees. 

10. Black Canyon of the Gunnison is so deep that sunlight only reaches the floor for 33 minutes each day






Instead of being named after the color of its rocks—as one might think—this Colorado national park is called "Black Canyon" for the way the sunlight hits it. Because the canyon walls are 2,722 feet tall in the deepest part, the rays only reach the very bottom for 33 minutes each day.