Most people are familiar with the drawings in Peru’s Nazca Desert:

It’s thought they were created by local peoples between 200 B.C. and 600 A.D. They’re remarkably well realized, considering that the builders probably couldn’t have viewed them from the air. Here’s a view from a satellite:

It’s easy to decide that they’re the work of visiting extraterrestrials — the airliners that first spotted them in the 1920s described them as “primitive landing strips” — but researcher Joe Nickell has shown that a small team of people can reproduce a drawing in 48 hours, without aerial supervision, using Nazcan technology. Still, well done.
(Top image: Wikimedia Commons)