A sizable building dating from thousands of years ago has been discovered in the ancient city of Petra in Jordan. The discovery was made from satellite images, added by observations carried out by drone aircraft, and fine-tuned with measurements taken by researchers on the ground.

Two sides of the monument are as long as an Olympic-sized swimming pool, while the adjacent sides measure twice that length. The structure encompasses a large ceremonial platform encircled by flagstones. On one side of this platform, evidence exists showing the area once contained a tremendous staircase, along with a row of columns. A square building, measuring 28 feet (8.5 meters) long on each side, once adorned the platform, with its door opening to the east. The site is located just half a mile from the center of the 2,500-year-old city and is unlike any other known structure in the area.

Pottery found in the area dates to about 2,200 years before our present day.

Archaeologists were surprised to find this relic hiding in plain sight in the southern Jordanian city. This historic region has been well explored since Johann Burckhardt first explored the region in 1812.

"I'm sure that over the course of two centuries of research [in Petra], someone had to know [this site] was there, but it's never been systematically studied or written up. I've worked in Petra for 20 years, and I knew that something was there, but it's certainly legitimate to call this a discovery," said Christopher Tuttle of the Council of American Overseas Research Centers.

Images of the archaic structure first revealed a faint outline sitting under the landscape, and detail was filled in by later observations. As additional structures from this ancient time are found, researchers will learn more about the cultures and customs of people who lived 22 centuries before the modern age.

Petra was once home to a group of people known as the Nabataeans, and the city remains a tourist attraction, playing host to hundreds of thousands of people annually.

Investigators believe the monument was likely abandoned sometime during the seventh century CE, at the end of the Byzantine period. In its heyday, the structure may have been used as a public facility, perhaps for ceremonial purposes. If so, this would be the second largest ancient structure of its type known in the world.

Discovery of the ancient site and analysis of the structure is profiled in the bulletin of The American Schools of Oriental Research.

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