Archaeologists have been granted permission to fly over Saudi Arabia to investigate hundreds of mysterious, seemingly ancient man-made structures.
Some of the rocky ‘gates’ are four times the length of a football pitch, and were spotted on Google Earth.
Some experts have suggested that they may be thousands of years old.
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David Kennedy of the University of Western Australia first spotted the structures in Google Earth imagery in a region of Saudi Arabia called Harrat Khaybar.
Kennedy said, ‘Last month, they lifted this veil of sorts and allowed me to fly over the country’s vast array of archaeological sites for the first time.
‘We planned where we wanted to fly in order to capture several thousand structures in these two lava fields. Our helicopter survey was probably the first systematic aerial reconnaissance for archaeology ever carried out in Saudi Arabia.’
The archaeologists refer to them as ‘gates’ because of how they look like garden gates from above – but their purpose, and age, remains unknown.
Kennedy previously wrote, ‘Gates are found almost exclusively in bleak, inhospitable lava fields with scant water or vegetation, places seemingly amongst the most unwelcoming to our species.’
Some of the gates are sufficiently old that lava flows appear to go over them.
The gates are up to 1,700 feet long, Kennedy writes.