For centuries, the Rub' al-Khali desert near Saudi Arabia and Dubai — known as the Empty Quarter — was dismissed as a lifeless sea of sand.

But now, it's revealing an astonishing secret.

In 2002, Sheikh Mohammed bin Rashid Al Maktoum, ruler of Dubai, spotted unusual dune formations and a large black deposit while flying over the desert.

That led to the discovery of Saruq Al-Hadid, an archaeological site rich in remnants of copper and iron smelting, which is now believed to be part of a 5,000-year-old civilization buried beneath the sands.