Inscriptions on rose-colored sandstone in the Nabataean archaeological site of al-Hijr near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

Inscriptions on rose-colored sandstone in the Nabataean archaeological site of al-Hijr near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

A jounalist walking past a tomb at Madain Saleh, a Unesco World Heritage site near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

A man walking past tombs carved into rose-colored sandstone in Madain Saleh, a Unesco World Heritage site near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

A journalist taking a photo of a tomb at Madain Saleh, a Unesco World Heritage site near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

A journalist taking a photo of a tomb at Madain Saleh, a Unesco World Heritage site near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

A man standing outside the Qasr al-Farid tomb (The Lonely Castle) carved into rose-colored sandstone in Madain Saleh, a Unesco World Heritage site near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

A man standing outside the Qasr al-Farid tomb (The Lonely Castle) carved into rose-colored sandstone in Madain Saleh, a Unesco World Heritage site near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

Tourists visiting the Khuraiba archaeological site near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

A date farm amidst sandstones in the Khuraiba archaeological site near the northwestern Saudi town of al-Ula. Photo courtesy: AFP

A date farm amidst sandstones in the Khuraiba archaeological site near the northwestern Saudi town of al-Ula. Photo courtesy: AFP