Thousands of monumental structures built from walls of rock in Saudi Arabia are older than Egypt's pyramids and the ancient stone circles of Britain, researchers say – making them perhaps the earliest ritual landscape ever identified.

A study published Thursday in the journal Antiquity shows that the mysterious structures dotted around the desert in northwestern Saudi Arabia – called "mustatils" from the Arabic word for "rectangle" – are about 7,000 years old. That’s much older than expected, and about 2,000 years older than either Stonehenge in England or the oldest Egyptian pyramid.

“We think of them as a monumental landscape,” said Melissa Kennedy, an archaeologist at the University of Western Australia in Perth and an author of the study. “We are talking about over 1,000 mustatils. These things are found over 200,000 square kilometers [77,000 square miles], and they’re all very similar in shape ... so perhaps it’s the same ritual belief or understanding.”