With a film crew, the team excavated the newly uncovered grave in August. But the real surprise was what was in the grave. Although many tombs discovered at Petra are found empty or disturbed, the chamber was filled with complete skeletal remains and grave goods made of bronze, iron and ceramic. The intact burial found beneath the Treasury provides rare insight into the lives of the Nabataeans, ancient Arab nomads whose desert kingdom flourished from the fourth century B.C. to 106 A.D., Creasman said.

“This is an extremely rare discovery; In the two centuries that Petra has been explored by archaeologists, nothing like it has ever been found before,” Gates said. “Even for one of the most famous buildings in the world… there are still enormous discoveries to be made.”

The significant discovery could be the largest collection of human remains found in one place in Petra, according to researchers, and was featured Wednesday during the season premiere of “Expedition Unknown.” (Discovery Channel is owned by CNN’s parent company, Warner Bros. Discovery.)

Petra was declared one of the New Seven Wonders of the World in the 2000s due to its unique architecture and the many mysteries that still surround the city. Although experts have debated the Treasury’s purpose for centuries, the most popular theory is that the monument serves as a mausoleum, although no skeletal remains have been found in the building itself, Gates said.

The Treasury receives hundreds of thousands of tourists each year, and has also been featured in several films, most notably as the location of the Holy Grail in the 1989 film ‘Indiana Jones and the Last Crusade’.

Among the artifacts were several vessels, with one skeleton holding a ceramic chalice resembling the shape of the Holy Grail. “It was really this great moment in history that imitated art,” Gates said.

The artifacts are extremely well preserved, Creasman said. Although the human remains are intact, they are in a more delicate shape than expected. Their condition could result from humidity and seasonal flooding in Petra, but also from the porous sandstone surrounding the tomb that retains moisture, he said. Some skeletons were found with mold.

Only a handful of tombs uncovered in Petra in recent decades have been found with untouched burials, Creasman said. Serious disturbances were most likely due to travelers seeking shade and shelter in the desert, he added.

The two graves uncovered under the left side of the Treasury 20 years ago by archaeologists from the Jordan Department of Antiquities contained partial skeletal remains, but the data has not been published, so it is unclear how many individuals have been found, Creasman said.

“We were hoping to find something that could tell us more about the ancient people and the place – human remains can be a very valuable tool in that regard,” Creasman said. “The burials in this grave are articulated, so the bones have not been jumbled around and moved, so that is extremely rare.”

One mystery surrounding the Nabataeans is their burial practices. In literature, Nabataean society is often described as more egalitarian, with the king more integrated with the lower classes than leaders of other civilizations, Creasman said. So far, of the Nabataean tombs found, there doesn’t seem to be a major difference between royal and regular burials, so it is difficult to say whether the recently discovered tombs under the Treasury were designed for royal burials.

The researchers also suspect that many of the textiles and jewelry commonly found in Nabataean burials, such as cloth wrappings and necklaces and other beads that adorned the bodies, were lost to the humidity and floodwaters that seeped into the grave, Gates said .

As researchers continue to study the skeletons, Creasman said they are hopeful that more details will come to light about who the people were in life. Researchers would like to to date the skeletons and artifacts and to use extracted DNA to determine whether the dozens of skeletons are related. Other analyzes could potentially help assess their diet and unravel whether they had a physical job, Creasman said.

“They must be hugely important people because where they are buried is such prime real estate; it really is the main entrance to the city,” Gates said. “I think learning who they are will really help unlock part of the Treasury Department story.”

Correction: An earlier version of this story incorrectly identified the four experts in the group photo. The story has been updated with the correct identifications.