Stonehenge was once thought to function as a kind of “Neolithic computer,” but archaeology has since debunked that idea. Current evidence now points to a different site: an arid hill in Peru’s Casma Valley, roughly 200 miles north of Lima.

There lies Chankillo, a complex constructed around 250 B.C.E., recognized as the earliest known solar observatory in the Americas. It stands as the clearest example of a monument designed to track the sun’s movements throughout the year, according to research published in Science. Though modest in appearance and largely absent from tourist brochures, Chankillo has garnered renewed interest as archaeologists release preliminary results from ongoing excavations.