The sky and the land, the clouds and the salt all meld together on the Salar de Uyuni. When the conditions are just right — during the wet season, when a thin layer of water coats the ground and the brilliant blue of the Bolivian sky is dotted with a few white clouds — the vast salt flat, the largest on the planet, seems to become the sky.

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Salar de Uyuni is a place of uncommon beauty, unchanged for thousands and thousands of years, in a country that is recognized as the poorest in Latin America.

It's also a place that contains one of the most sought-after metals in the world, which makes the ancient salt flats a type of modern-day battleground.

An ocean of white

The Salar of Uyuni with mountains in the backgroundThe Salar of Uyuni is so uniform and flat that it is routinely used to calibrate satellites. (Photo: Anouchka Unel/Wikimedia Commons)

The salar is notable for its utter vastness — it stretches for more than 4,000 square miles — its brilliant whiteness and its otherworldly flatness. Largely because of seasonal rains that form ponds that dissolve any mounds and bumps in the salty surface, the salar (Spanish for "salt flat") changes less than a meter in height from one side to the other. It's so uniform that it's used to calibrate altitude by satellites.

"It's as if you’re on a white ocean with no waves," Adrian Borsa, a geophysicist, told Nature in 2007. "You see the horizon, the curvature of Earth. It's absolutely featureless."

The salar was formed in the high plateau, more than two miles above sea level, when the Andes mountains took shape eons ago. Rains filled flat spots with lakes. The lakes eventually dried up, and salars were born.

The whiteness of the salty floor, a few feet thick in some places, is not completely unbroken. There are a few islands, the biggest named Isla Incahuasi ("Inca house"), once the top of an ancient volcano. It's now a rocky, cactus-strewn rest stop for tourists in the middle of the salar.

Cacti and rock along the edges of the Isla Del Pescado on the Salar De UyuniThe Salar De Uyuni isn't the most habitable area, but some hearty plants and animals do thrive there. (Photo: Wikimedia Commons)

Other than the cactus, the salar features little as far as plants and vegetation goes. The main animals in the area are some Andean foxes, rabbit-like rodents known as viscachas and a few different species of pink flamingoes, who breed in the Salar de Uyuni every November.

One other notable feature of the landscape: the cones of salt that dot the surface of the salar. Salt is exported and used to, among other things, make bricks. Though Salar de Uyuni is reported to have 10 billion tons of salt, only 25,000 tons are taken each year.

The most valuable feature is beneath the surface.

A treasure underneath

Salar de Uyuni flatsThe true value of the Salar de Uyuni isn't its salt but its buried lithium. (Photo: Pedro Szekely/Wikimedia Commons)

In the brine under the crust of salt at Salar de Uyuni lies the world's largest reserve of lithium. The soft metal is a key component in lithium batteries, used to power everything from your cell phone to new electric cars. By some estimates, the lithium battery market — sparked by a worldwide push toward electric vehicles — could be worth more than $22 billion in 2016.

According to one U.S. Geological Survey estimate, Bolivia has more than 9 million tons of lithium, most of it in the Salar de Uyuni. That may be more than 50 percent of the world's reserve. Those numbers are disputed, but at even half that, Bolivia could build — if it chooses to do so — the largest lithium-mining operation in the world, bigger than that of its neighbor Chile. That would enable the country to take over the mantle of "The Saudi Arabia of Lithium."

A plant for lithium processing on the Salar de UyuniThis plant on the Salar de Uyuni will extract the lithium carbonate from the nearby plains. (Photo: Aizar Raldes/AFP/Getty Images)

Bolivia's per capita income is less than $3,000 a year, so Bolivia president Evo Morales has made building a lithium industry high on his list of priorities. The country opened its first, minor-scale lithium operation in 2013. In April, Morales pledged to invest $617 million toward more development.

Morales and his administration have worked with other countries — many in Europe, some in Japan and China and elsewhere — looking for those who want in on the country's windfall. It's a risky proposition, though, fraught with political, economic and environmental perils. Morales is refusing to bow to foreign investors unless they agree to build battery-producing plants in Bolivia and unless they cut the country in on 60 percent of revenues.

A decision for Bolivia

A man looks up into the sky while standing on the Salar de Uyuni while the sky is reflected on the groundThe Salar de Uyuni is a natural wonder, but the drive to harness its resources could tarnish it. (Photo: Ezequiel Cabrera/Wikimedia Commons)

There is pressure on Bolivia inside and out, from those who want in on a possible economic windfall, from those who disagree how it should be handled, even from those who resist it, who see it as another empty promise.

"There are salt lakes in Chile and Argentina, and a promising lithium deposit in Tibet, but the prize is clearly in Bolivia," a Mitsubishi executive told the New York Times. "If we want to be a force in the next wave of automobiles and the batteries that power them, then we must be here."

For many Bolivians — perhaps most for those who live around the cold, harsh and beautiful Salar de Uyuni — the idea of change in a place that hasn't changed in centuries is hard to fathom.

"Many Bolivians are willing to not go forward," Larry Birns, the director of the Council on Hemispheric Affairs, told a group in 2013 when the first lithium plant was opened. "They feel, 'We're not really going to benefit from this anyway. We never have.'"