(CNN)The ancient city of Petra may be one of the world's best-known archaeological sites, but it still has secrets to reveal.
'Massive' monument found in ancient Petra
A massive "monumental platform" has been discovered within the Petra UNESCO World Heritage Site in what is now part of southern Jordan.
Archaeologists Sarah Parcak, a National Geographic fellow, and Christopher Tuttle, executive director of the Council of American Overseas Research Centers, used satellite imagery, drones and ground surveys to find the structure and document its location.
Their study, which was published in a recent "Bulletin of the American Schools of Oriental Research," was first reported by National Geographic.
The newly discovered platform, which measures about 56 x 49 meters, appears to be a unique feature that has "no parallels at Petra or in its hinterlands at present," according to the study.
"When National Geographic fellow Sarah Parcak shared the results of her latest research with us, we knew it would pique global interest given the historic significance of this treasured site," said Kristin Romey, archaeology writer for National Geographic.
"It's really a remarkable find for the archaeological community," she said.
Some half a million tourists already visit the ancient city and its surroundings, and thousands of monuments and structures have already been documented within the city center.
Occupied since prehistoric times, the lost Nabataean civilization made this part-carved, part-built city their capital and a major caravan center of trade from the fourth century BC to the first century AD.
The combination of Hellenistic architecture with traditional Nabataean rock-cut temple/tombs can be seen in the city's Deir ("monastery"), the Urn Tomb, the Palace Tomb and the Corinthian Tomb.
The newly discovered platform was probably built during the second century near the city center when the Nabataean civilization was flourishing, and it appears "highly likely that the platform and structures were initially constructed to serve ceremonial purposes."
That ceremonial focus probably allowed the site's conversion to a Christian chapel during the Byzantine period. During later Islamic periods, ordinary uses were more likely.
A smaller platform measuring about 46 × 44 meters was constructed within the larger platform, with one side of the smaller platform fronted by a row of columns.
"The row of columns crowned a monumental stairway that spanned the entire width of the smaller platform, " according to the study.
The city center is part of Jordan's Petra Archaeological Park, which covers 264,000 square meters within Wadi Musa in Jordan.