Cave art in the Americas is rare and usually small compared to some of the giant paleolithic paintings of Eurasia, but a new discovery reveals an exception. The ceiling of the cave in question, whose name and location have been kept a secret, is covered with images, some very large, but the height is so low observers have not been able to take them in. By sticking together overlapping photographs, archaeologists have revealed all, but left open the questions of why the artists chose a location where their work could not be seen, and how they kept their work cohesive.

America's largest cave paintings are concentrated in the US southwest. However, studies of a site – known as 19th Unnamed Cave, Alabama, to prevent damage from the inquisitive – reveal the southeast may have a lot more than has been recognized.

The art has been reconstructed using 3D photogrammetry – where each photograph heavily overlaps its neighbor to enable reconstructions – and is described in Antiquities. University of Tennessee Knoxville Professor Jan Simek and co-authors needed the photogrammetry because the chamber in which the artwork lies is mostly between 0.6 and 1.25 meters (2-4 feet) high, so even lying on the ground the ceiling is too close to see the larger works at one time.

The 3D model created from the photogrammetry is much more flexible. “Manipulation of the distance between the viewer and the ceiling of the glyph chamber reveals myriad human and animal figures that could not be seen in situ due to their size and the viewer’s physical proximity,” the paper notes.

Among other things, the photogrammetry reveals a life-size human figure wearing what may be a ceremonial cloak and headdress and holding distinctive shapes in each hand. An even taller figure, although less completely drawn, also appears to represent a human in regalia.

In total, 400 square meters (4,000 square feet) of the cave ceiling is covered, in some cases with multiple layers painted over each other. Like cave art in Eurasia, there is a mix of abstract shapes, animals, and figures with human shapes (anthropomorphs). The largest is a 3.4 meter (11 foot) long serpent patterned to resemble the eastern diamondback rattlesnake (Crotalus adamanteus), sacred to the Indigenous people of the area. Although some pre-colonization open-air rock art from the southwest is larger than the anthropomorphs, the snake is the largest single cave painting found in the Americas. Its placement makes it look as if the snake is emerging from a crack in the rocks, making it appear even larger.

The anthropomorphs “are not recognisable characters from ethnographically recorded Southeast Native American stories,” the paper notes. “They probably depict characters from previously unknown religious narratives, likely of the Middle Woodland period.”

The art itself can't be dated, but a piece of charcoal and some river cane found on the floor are approximate 1,200 and 1,700 years old, respectively. Ceramic sherds found there are of a style popular in the area 1,000-3,000 years ago. It seems likely the items were left at the time the art was made.

Perhaps the most remarkable feature of the art is that the artists would have faced the same problems of perspective that viewers do. “The makers had to create the images without being able to see them in their entirety,” the paper notes. Yet so strong is the human urge to make art, that they were undeterred.