There are thousands of aligned holes in Peru. Archaeologists now think they know who created them

A series of about 5,200 holes stretching nearly a mile (1.5 kilometers) across the Pisco Valley in the southern Peruvian Andes has baffled researchers for nearly a century. But a fresh look at the site, called Monte Sierpe, or “serpent mountain,” may help archaeologists to decipher why ancient people constructed it hundreds of years ago.

The “band of holes,” as it’s informally called, first garnered attention when National Geographic published aerial photos of the site in 1933.

But there are no written records relating to the formation, leaving its purpose open to interpretation — and there have been many. Hypotheses about the holes’ use have included defense, accounting, storage, gardening, water collection, and fog capturing purposes. People who support ancient astronaut theory, a belief that aliens are real and shaped early civilizations on Earth, have also suggested extraterrestrial connections.

Now, new drone footage and a microbotanical analysis of pollen grains found within the holes are leading researchers to suggest that the site first served as a bustling marketplace for a pre-Inca civilization, and later as a method of accounting for the Incas, according to a study published November 10 in the journal Antiquity.

“Why would ancient peoples make over 5,000 holes in the foothills of southern Peru?” said lead study author Dr. Jacob Bongers, digital archaeologist at the University of Sydney and a Visiting Research Fellow at the Australian Museum Research Institute. “We don’t know why they are here, but we have produced some promising new data that yield important clues and support novel theories about the site’s use.”