There’s long been speculation of underground chambers below the monument known as the Khaznah, or the Treasury, in the ancient city of Petra, Jordan — and now it’s been confirmed.

Archaeologists recently discovered a tomb with at least 12 human skeletons and artifacts, estimated to be at least 2,000 years old, CNN reported.

The elaborate monument, carved into pink sandstone cliffs, has been featured in several movies — it’s most well-known as the site of the Holy Grail in the 1989 film “Indiana Jones and the Last Crusade.”

In 2003, two tombs were found below the left side of the monument on an expedition led by Dr. Pearce Paul Creasman and other archaeologists, leading to theories that they weren’t the only ones.

Creasman, executive director of the American Center of Research, and his team used a remote sensing technique called ground-penetrating radar, which uses pulses to detect underground objects to see if the physical features on the left side, where the first two tombs were found, matched the features on the right.

They found strong similarities between the two sides, giving them the proof they needed to get permission from the government in Jordan to start digging.

“I think we’ve got something,” Creasman told Josh Gates, host of Discovery Channel’s “Expedition Unknown,” according to CNN.

They excavated the newly uncovered tomb in August with a film crew — but the most shocking discovery was what was inside it.

Most tombs uncovered in the ancient city are either empty or disturbed, but this one was filled with complete skeletal remains and grave goods made from bronze, iron and ceramic.

Researchers said that the finding might be the largest collection of human remains found in one place within Petra.

The pair of tombs uncovered two decades ago by archaeologists from the Jordan Department of Antiquities had partial skeletal remains, although it’s unclear how many were found because the data was not published, Creasman said.

“This is a hugely rare discovery — in the two centuries that Petra has been investigated by archaeologists, nothing like this has been found before,” Gates said. “Even in front of one of the most famous buildings in the world … there are still huge discoveries to be made.”

Among the well-preserved unearthed artifacts were several vessels — and one skeleton was found holding onto a ceramic chalice that resembled the mythical Holy Grail that Jesus drank from at the Last Supper.

“It really was this awesome moment of history imitating art,” Gates said.

Though the human remains were intact, they were more fragile than expected — some discovered with mold — potentially due to the humidity and seasonal floods, as well as the porous sandstone surrounding the tomb entrapping moisture, Creasman said.

With the burial intact, this gave the archaeologists rare insight into the Nabataeans, ancient Arabian nomads whose desert kingdom thrived during the 4th century BC to AD 106, Creasman explained.

“We were hopeful to find anything that might tell us more about the ancient people and place — human remains can be a really valuable tool in that regard,” Creasman said. “The burials in this tomb are articulated, so the bones haven’t been rummaged around and moved, so that’s exceedingly rare.”

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