Experts are still unsure as to the purpose of the structures, but some of them were found to be draped over lava domes – a mound shaped area where lava has dried near volcanoes.
The stone walls, which have been called "gates" as they resemble field gates when viewed aerially, were found in a region in west-central Saudi Arabia called Harrat Khaybar.
David Kennedy, a professor at the University of Western Australia, who helped to discover the gates through satellite imagery, said they "are stone-built, the walls roughly made and low."
He adds that they "appear to be the oldest man-made structures in the landscape," and that "no obvious explanation of their purpose can be discerned".
The size of the gates varies massively, with the smallest being 43 feet and the largest stretching to 1,699 feet.
Prof Kennedy adds: "Gates are found almost exclusively in bleak, inhospitable lava fields with scant water or vegetation, places seemingly amongst the most unwelcoming to our species."