Thanks to 3D modeling techniques, the largest cave figures in North America have been discovered in a cave in Alabama that also contains hundreds of pre-contact Native American mud glyph drawings.

In a study published on Tuesday in the journal Antiquity, researchers revealed that the very large anthropomorphic glyphs featured on the cave’s ceiling were surprising as they were not at all apparent at the original site due to their state and the tight confines of the cave.

The carvings were only possible to perceive through digital manipulation of the chamber space after the 3D modeling of the cave was initiated in 2017, originally aimed to record the cave’s many other carvings in case get damaged or fade.

The archaeologists raved about the technology that allowed for the discovery and argued that photogrammetry offered “untapped potential for not simply the documentation but also the discovery of a variety of archaeological phenomena.”

An anthropomorph in regalia from an unnamed cave in Alabama, U.S., in combination with an artist’s illustration. (Photo courtesy of Antiquity Journal)

The carvings have been estimated to be made around 1,000 years ago by artists who, working by the light of burning reeds, carved figures into the ceiling of the cave in what’s now Alabama, crouching in the narrow space below.

As time passed, the carvings have become almost invisible to the naked eye due to the mud that naturally accumulated on the cave’s walls.

The carvings, some of which extend up to 2 meters (7 feet) long, depict various figures, including what appears to be people wearing Native American regalia and garments such as headdresses and carrying what appears to be a rattle.

The large figures are thought to represent spirits of the underworld, their power and importance expressed in their shape, size and context.

“They are either people dressed in regalia to look like spirits, or they are spirits,” archaeologist Jan Simek, a professor of anthropology at the University of Tennessee in Knoxville and the lead author of the study, told NBC News. “The term we like to use is that they were ‘materializing’ those spirits through the costumes that they wore,” he said.

An enigmatic figure of swirling lines, with a round head at one end and a possible rattlesnake tail at the other, from an unnamed cave in Alabama, U.S., in combination with an artist’s illustration. (Photo courtesy of Antiquity Journal)

The cave in the northern Alabama countryside is the richest prehistoric cave art site in North America, Simek said, as he and the team continue to keep its precise location a secret.

Another carving features a curled up snake that experts largely believe is a diamond rattlesnake.

The rich cave in question was discovered in the 1990s by Atlanta-based caver Alan Cressler, another co-author of the new paper, Tennessee-based photographer Stephen Alvarez, a co-author of the study, said.

Several years later, Alvarez had the idea to document the cave’s carvings with photogrammetry so they could have better grasp of its carvings. When he did so, “not only could we see engravings, but there were hundreds, if not thousands more than we had realized,” he said.

Photographic photogrammetry allows researchers to create photographic models of the subject. The technique combines digital photographs with 3D computerized models of a particular space.

The latest study comprises more than 14,000 photographs. Many more are likely to be found.