CRAWLEY, AUSTRALIA—David Kennedy of the University of Western Australia and his colleagues discovered nearly 400 low stone walls in west-central Saudi Arabia with satellite imagery, according to a report in Live Science. Most of the walls, which resemble field gates, had been built in the lava fields of Harrat Khaybar. Some were covered with lava flow, or were even placed on the sides of old lava domes. Kennedy said the smallest of the gates is about 43 feet long, while the longest is about 1,700 feet long. Some of the structures are rectangular-shaped, while others are “I” shaped, or have one stone wall with piles of stones at each end. The gate-like structures may be about 7,000 years old, and are thought to be older than other stone structures in the lava fields, such as those known as kites, which are thought to have been used in hunting. For more on archaeology in the region, go to “Expanding the Story.”