A vast 4,500-year-old network of ‘burial avenues’ lined with well-preserved Bronze Age tombs has been discovered in Saudi Arabia.

In a new paper, researchers detail the layout of around 18,000 graves, spanning thousands of kilometers in Saudi Arabia’s Al-‘Ula and Khaybar counties.

They consist of small stone piles arranged in elaborate shapes, marking the spot where individual individuals or small groups were buried, experts say.

The burials are described as ‘hanging’ graves because they resemble circular pieces of jewelery attached to a chain or ‘tail’.

Hanging tombs are already known to have yielded human remains dating back to the mid-third millennium BC, during the Bronze Age.

In all, experts have observed around 18,000 graves along ‘burial avenues’ – long-distance ‘corridors’ linking oases and pastures bordered by burials – only 80 of which have been sampled or excavated.

It is believed that the tombs may have been built as monuments (‘cenotaphs’) or for other symbolic or ritual purposes not yet clear.

Dr. Matthew Dalton, from the School of Humanities at the University of Western Australia, is the lead author of the findings.

He and his team used satellite imagery, aerial photography from helicopters, ground surveys, and excavations to locate and analyze the burial avenues.

“People living in these areas have known about them for thousands of years,” said Dr. Dalton. CNN.

“But I think it wasn’t really known until we got satellite images of how widespread they are.”

The desert regions of the Arabian Peninsula and the Levant are known to be traversed by countless roads, flanked by stone monuments, the vast majority of which are ancient tombs.

Thousands of miles of these pathways and monuments, known collectively as “burial avenues,” can be traced across the landscape, especially around and between major perennial water sources.

Funeral avenues were the major road networks of their day, according to Dr. Dalton.

Its current existence shows that the populations living on the Arabian Peninsula 4,500 years ago were more socially and economically connected to each other than previously thought.

The researchers found that the highest concentrations of funerary monuments on these avenues were located near permanent water sources.

The direction of the avenues indicated that the populations used them to travel between the main oases, including Khaybar, Al-‘Ula and Tayma.

Minor avenues fade into the landscapes surrounding the oases, suggesting that the routes were also used to move herds of domestic animals to nearby pastures during periods of rain.

“These oases, especially Khaybar, exhibit some of the densest concentrations of funerary monuments known anywhere in the world,” said Dr Dalton.

“The large number of Bronze Age tombs built around it suggests that populations had already begun to settle more permanently in these favorable locations at this time.”

Continued excavation and analysis of the human remains within these monuments will be essential in the future, according to the researchers.

“Primary burials, when identifiable and properly preserved, can reveal the demographics of those for whom the avenue monuments were originally built, allowing for a better reconstruction of these societies and their burial practices,” they state.

The findings have been published in the journal the Holocene.