There’s nothing quite like an ancient archaeological mystery to get the imagination going. Just this week, archaeologists working in Saudi Arabia announced the discovery of a mysterious set of stone structures in the middle of Harrat Khaybar, an ancient volcanic field in the central Arabian desert. 400 separate structures have been found, and the researchers who found them are calling them “gates” based on how they appear from above. The gates were mostly found through studying satellite imagery, as no record of them exists in any archaeological or historical texts.
The 400 gates vary in size from just a dozen meters long to well over 500 meters long. When they were built, the gates would have consisted of long, low stone walls. Many are in disrepair today, but some still stand a few meters off the ground. David Kennedy, a professor at the University of Western Australia and one of the archaeologists who discovered the gates, told LiveScience that the gates “appear to be the oldest man-made structures in the landscape" and that "no obvious explanation of their purpose can be discerned."
Kennedy says that while they have little concrete evidence for the gates' purpose(s), similar gates have been found in other inhospitable regions on the planet where little water or vegetation are found, possibly suggesting that they had an agricultural or irrigational purpose.
Kennedy and his fellow researchers will publish their findings in the November issue of Arabian Archaeology and Epigraphy, but also plan to conduct extensive fieldwork in the future to try and determine what the gates might have been used for and when exactly they were built. Could these structures have been for some unknown ritual or ceremonial purpose or, at the most imaginative end of speculation, could they have been used as landing strips for ancient aliens (if they ever existed at all, that is)? Most likely, they were they some sort of agricultural or livestock enclosures, but until more research is conducted, any guess is as good as any at this point.