Long known of but little-understood, Jordan's "Big Circles" are around 400 meters in diameter and remain a compelling mystery.
Their purpose is unknown, and archaeologists are unsure when these structures were built. Analysis of the photographs, as well as artifacts found on the ground, suggest the circles date back at least 2,000 years, but they may be much older. They could even have been constructed in prehistoric times, before writing was invented, scientists say.
New satellite imagery revealed at least two more circles, bringing the total to 13; one, in Syria, was recently destroyed. Though the circles were not hard to create, comprising of only a single low stone wall, they would have been ineffective animal corrals and their sheer enormity would have required extensive planning.