Although the Sahara Desert makes an impression when it comes to size, it actually holds secrets that make it one of the most fascinating and vibrant locations on the entire planet. Here are 10 things you probably never knew about this remarkable location.

It's Actually the Third-Largest Desert

The hot sand dunes of the Sahara nestled in silence beneath the cloudy sky
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Antarctica, which is 5.5 million square miles, and the Arctic, which is 5.4 million square miles, are considered to be polar deserts since their low air temperatures don't hold a lot of moisture, yet they still appear wet since it's too cold for any precipitation that does occur there to melt. The 3.5 million square miles of the Sahara, on the other hand, encompass the world's largest "hot" desert, which spans across 11 northern countries on the continent of Africa. The entire region is the size of the United States and is bordered on the east by the Atlantic Ocean, the west by the Red Sea, the north by the Mediterranean Sea, and the south by the Sahel savanna.

It Was Once a Savanna

Sunset over the savanna in Kenya, perhaps what the Sahara used to be like
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Although most of the region's known history only included human habitation in the verdant Nile Valley, an abundance of rainfall in the area led to settlements that have now been documented at 150 different locations across the vast region roughly 10,500 years ago. Permanent freshwater lakes were home to fish as large as six feet long and dairy farms produced yogurt, cheese, and milk. This period lasted until around 5,300 B.C. with a full return to the current dry conditions around 3,500 B.C.

Its Dust Travels as Far as the Amazon

Aerial view of the lush green Amazon where mineral dust can be found from the Sahara Desert
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Just north of Lake Chad sits the Bodélé Depression, one of the most powerful wind tunnels in the world. Situated in a gap between the Tibesti and Ennedi mountains, this mineral-rich basin sends a phenomenal 40 million tons of dust westward each year along the equatorial trade winds to the Amazon Rainforest. When this massive dust storm finally settles at its far-off destination, it replenishes the nutrients that are depleted by the region's tropical rains.

Sand Dunes Make up Only 15% of It

Shadows stretching out from the sand dunes, covered in wind ripples
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While many people picture the Sahara with never-ending stretches of windswept sand dunes, the famous desert actually includes numerous diverse geographic features. These include stony gravel plains known as regs, basins, and depressions with salt lakes and flats, high, hardy plateaus called hamadas, and even inactive volcanoes that form the Tibesti mountain chain in northern Chad. The highest peak is the 11,200-foot Emi Koussi and the lowest spot is Egypt's Qattara Depression situated 435 feet below sea level. For those interested in touring the world-renowned dunes, two of the most celebrated are Morocco's Erg Chigaga and Erg Chebbi.

The "World's Toughest Footrace" Is Held in Morocco

Person walking along the top of a sand dune
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For the past 34 years, the most rugged racers from around the globe have met to compete in a seven-day test of endurance that combines the distance of six marathons with daunting desert dust storms, boundless dunes and plains, jagged rock-strewn terrain, and temperatures that exceed 120 degrees Fahrenheit. The Marathon des Sables' exact route is always a secret until the day before and racers must carry all their food and water with them on their backs before bedding down each night in communal Berber tents made of goat hair. Those who finish receive newfound status as a hero and memories to last a lifetime.

It's Home to a Plant That Can Survive 100 Years Without Water

Single small plant in the Sahara desert
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Known as the Sahara resurrection plant due to its unique ability to go into a state of dormancy without excessive cell damage, this plant curls its branches into a ball and uses wind flow to roll around the sand until it finds a hydrated oasis where it can bloom again. Scientists say that this rare ability to revive after experiencing up to 95% water loss comes from its capacity to shut down photosynthesis so that cell proteins, lipids, RNA, and DNA are protected during the long Saharan dry spells.

Mauritania Houses Five Ancient Libraries

Village at the bottom of hills with palm trees in Mauritania, Africa
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The oldest of the five libraries is La bibliothèque el Habot, which is home to numerous texts on astronomy, religion, mathematics, medicine, and poetry that purportedly date as far back as the 10th century A.D. and are preserved in a dwelling still owned by the descendants of the original builders. The entire city has been named a UNESCO World Heritage Site for its remarkable resilience amid the harsh dry climate, its status as one of the seven holy cities of Islam, and its determination to preserve the priceless manuscripts that have transformed this old caravan trading route town into an oasis of historical treasures.

There's an International Festival of the Sahara

People ride on camels with a guide in the Sahara right outside of Douz, Tunisia
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This annual celebration takes place in the lush oasis town of Douz, Tunisia, which is said to have 25 palm trees for each of its 12,000 residents. Known as the "Gateway to the Sahara," the city hosts the annual festival to celebrate indigenous Berber and Arab art and traditions of northern Africa. Roughly 50,000 people gather each autumn to enjoy activities in the desert such as camel races, sand dune skiing, go-carting, and pickup sand hockey. Breathtaking performances include traditional belly and nakh (hair) dances, poetry readings, live folk music, theater acts showcasing the region's rich warrior traditions, and craft and food bazaars.

There Are Mysterious Structures in the Western Sahara

View of rock formations in the distance in the Sahara desert
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In a compact 3.5 square miles of land located between the Atlantic Ocean and Atlas Mountains in the Western Sahara, 400 stone monuments were rediscovered between 2002 and 2009. These fascinating and diverse structures sit just north of the village of Tifariti and include intriguing stone circles, platforms, long straight lines of rock known as goulets, curving rock walls, and two large piles believed to be burial sites dating back at least 1,500 years. Since the Tifariti Wadi (streambed) is located nearby, archaeologists believe this could have been the location of a complex ancient settlement.

An Art Display Can Be Seen From Space

Aerial view of El Gouna, where the Sahara desert meets the red sea
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"Desert Breath" in El Gouna, Egypt was created by a trifecta of artists who were inspired by the immensity of the Red Sea meeting the enormity of the Sahara Desert. The epic creation's conical-shaped dunes and depressions are meant to reflect the tension between the positive and negative water content in each of these two natural wonders. Their layout in continuous interlocking spirals reflects the infinity of the desert. The amazing artwork doubles as a walking path for those visiting the mountains and sea and is so vast at 62 square miles that it can be seen from space. "Desert Breath" was meant to slowly fade back into the landscape around it to mark the passage of time — making it one of the most unique environmental masterpieces in the world.