The oldest solar observatory in the Americas has been discovered in coastal Peru. The 2,300-year-old ceremonial complex featured the Towers of Chankillo, 13 towers running north to south along a low ridge and spread across 980 feet (300 meters) to form a toothed horizon that was used for solar observations.

Researchers excavated the solar observatory between 2000 and 2003. They found buildings—in exact mirror position of each other—to the east and west of the towers with observation points for watching the Sun rise and set over the toothed horizon.

Full report here: Ancient solar observatory discovered in Peru