Researchers have discovered huge 4,000-year-old fortifications in northwestern Saudi Arabia, according to the Journal of Archaeological Science: Reports. The oases of the North Arabian desert were inhabited by a sedentary population in the 4th and 3rd millennia BC. The fortification surrounding the Khaybar oasis, one of the oldest known structures from this period, was discovered by a team of researchers from CNRS1 and the Royal Commission for AlUla. This newly discovered walled oasis near Tayma is one of the two largest oases in Saudi Arabia, Planet Today reports. Although several walled oases dating back to the Bronze Age have been previously documented, this important discovery sheds new light on the human footprint in northwestern Saudi Arabia. This archaeological discovery paves the way for the discovery of the prehistoric, pre-Islamic, and Islamic conquests in the northwestern part of the Arabian Peninsula.