Archaeologists have used satellite imagery and drone photography to discover an enormous ceremonial platform near the center of the ancient city of Petra. Sarah Parcak and Christopher Tuttle published their finding in a new report that reveals the monument that has been, as the paper is titled, hiding in plain sight. That is all the more impressive because of the platform’s size: at 184 by 161 feet, it’s roughly the length of an Olympic swimming pool (and twice the width), National Geographic reports.

“I’m sure that over the course of two centuries of research [in Petra], someone had to know [this site] was there, but it’s never been systematically studied or written up,” Tuttle told the magazine. “I’ve worked in Petra for 20 years, and I knew that something was there, but it’s certainly legitimate to call this a discovery.” READ MORE