Ever since Swiss explorer Johann Burckhardt became the first westerner to rediscover the ruins of Petra in 1812, archaeologists have flocked to the ancient desert city with trowels and spades in hand. Although archaeologists have documented thousands of carved and constructed monuments at the UNESCO World Heritage site, a pair of researchers has proven that Petra has yet to reveal all of her secrets.

In a newly published study in the latest issue of the Bulletin of the American Schools of Oriental Research, University of Alabama at Birmingham archaeologist Sarah Parcak and Christopher Tuttle, executive director of the Council of American Overseas Research Centers, report that they have found a massive stone monument “hiding in plain sight” at Petra. For two centuries, tourists and archaeologists alike had no idea what was hidden right underneath their feet in the sands of the ancient capital of the Nabataean kingdom, which was abandoned in the 7th century. All the discovery took was a change of perspective, some high-tech tools and the eagle eye of Parcak—an archaeologist nicknamed the “Indiana Jones from Space.”

Aerial images of the monument found at Petra. (Credit: Bulletin of the American Schools of Oriental Research)

Parcak is a self-described “space archaeologist” who studies satellite imagery and uses complex algorithms to detect subtle changes in vegetation that signal man-made objects hidden from view on the ground. She has used satellite images to help locate 17 potential pyramids in Egypt, 1,000 lost tombs and 3,100 forgotten settlements. In order to test whether discoveries at well-known and well-surveyed archaeological sites around the world could be possible with a similar high-tech study, Parcak began to analyze high-resolution satellite imagery of Petra from Google Earth and the WorldView-1 and WorldView-2 satellites.

As Parcak studied a plateau less than a mile south of the city center of Petra, a huge rectangular outline came into focus. She passed her observations along to Tuttle in Petra, and he followed up with four ground surveys to take photographs, make detailed observations and collect measurements and GPS points. In addition, Tuttle launched a drone over the site to take aerial photographs, which were laid over the satellite images.

What the archaeologists had discovered was a massive, 30,000-square-foot platform—twice as big as an Olympic swimming pool—supported by substantial terrace walls and topped by a smaller 28-foot-by-28-foot platform, which was paved with flagstones and originally lined with sandstone drum columns on one side and a vast staircase on the other. Pottery found near the structure suggest that it could have been built as early as 2,150 years ago at a time when Petra was flourishing.

The discovery came as a surprise to Parcak. “We thought that maybe we’d find some small stone structures or roads,” she told NPR, “but we didn’t think at all that we would find anything large, just because Petra is a World Heritage site and it’s been worked on intensively for nearly 200 years.”

Aerial images of the monument found at Petra. (Credit: Bulletin of the American Schools of Oriental Research)

The archaeologists say the structure is unique in terms of its size, shape, location and orientation. “This monumental platform has no parallels at Petra or in its hinterlands at present,” Parcak and Tuttle wrote in the article. “The amount of effort to construct the site was massive, yet the focal building itself is quite small. The platform is located relatively close to the ancient city center but in a spot where easy access from the city center is not readily apparent.”

The researchers believe the platform may have had a ceremonial purpose, and the east-west alignment of the smaller structure may also have permitted its conversion to a Christian chapel during the Byzantine period. “We know it’s large, it’s significant, it’s important. It probably would have had some kind of a public function,” Parcak told NPR. “Could it be used for religious purposes? Was it some sort of public administrative structure? I wish I knew.” A possible excavation in the coming years might help to solve the mystery.

This study combining high-tech imagery analyses and a non-collection pedestrian survey was the first ever undertaken at Petra, and Parcak told the Boston Globe that the discovery demonstrates the need for archaeologists to employ more drones and satellite imagery to uncover ancient relics. “Even at very large and well-known World Heritage sites, we’ve taken a lot for granted in terms of what’s there,” she said. “It’s important to use these new technologies to really allow us to look at them with a fresh pair of eyes.”

The complete article can be found on JSTOR.