Al-Ula – A massive archaeological survey has been launched in Al-Ula county, in north west Saudi Arabia, as the Kingdom prepares to develop the area and open up to mainstream tourism. Covering nearly 9000 square miles (22,500 sq km), Al-Ula county has a dramatic desert landscape.
Al-Ula valley – Much of the survey is concentrated in Al-Ula valley, a historical oasis where date palms flourish.
Ancient Dedan – These tombs are carved into cliffs near Dedan -- the first major city built in Al-Ula valley. Now called Al-Khuraybah, Dedan prospered thanks to passing trade in valuable commodities including frankincense, myrrh and precious stones. It had its heyday around 500 BC.
Lion tombs – The lion carvings above these tombs near ancient Dedan indicate that high status people were buried here.
Mada'in Salih – The Nabataeans established their major southern city just north of Al-Ula valley. They carved spectacular tombs into rocky outcrops at Mada'in Salih, now a UNESCO World Heritage Site.
Al-Ula Old Town – Occupied from at least the twelfth century right up until the 1980s, Al-Ula Old Town contained around 900 houses and 400 shops made of stone and mudbrick.
Al-Ula Old Town – The labyrinthine streets were protected by a defensive wall.
Rock formations – Carved by the elements, some of Al-Ula's rocks have taken on surprisingly sculptural -- and human-like -- forms.
Elephant rock – Known locally as Jabal Al-Fil, Al-Ula's iconic elephant rock looks just like ... an elephant.
Cairn – The most common man-made structures are cairns -- piles of stones arranged on top of a grave, often surrounded by a circular wall. "When I first saw them from the air, I thought they must be only hundreds years old because they were so well preserved," says archaeologist David Kennedy. "But when we landed, we realized they were built thousands of years ago. They were built with such care that they are still intact."
Cairn – The cairns in Al-Ula's hinterland measure up to 65 feet (20 meters) in diameter.
Cairn and triangle – Some of the cairns have one or more associated triangular structures which point towards the grave.
Cairn and triangle – The triangles are a mystery -- archaeologists have no idea what they symbolize.
Triangle – Most take the form of isosceles triangles and have been constructed with great precision so that the longest point is directed towards the grave.
Gates – Some of the most enigmatic features in the landscape are "gates". So-called because they resemble field gates when viewed from the air, the structures consist of short, wide stone walls linked by long parallel walls.
Gates – Archaeologists are baffled by the gates. "There are no entry points and we don't know what they were used for," says David Kennedy.
Kite – "Kites" are another intriguing feature. It is thought that they were used to funnel herds of animals, such as gazelle, into a killing enclosure for slaughter.
Inscriptions – Some of Al-Ula's rocks and cliff faces are adorned with inscriptions written in a number of languages including Arabic (seen here), Aramaic, Nabataean, Greek and Latin.
Hunting scene – Other rock faces feature engraved art. In this scene ibex -- a type of wild goat -- are being hunted with bows and arrows.
Ostrich – This carving dates from the period before 6,000 BC, when ostriches lived in Al-Ula. Climate change records show that after this time, the landscape transitioned from savannah to desert. As the environment dried up, the ostriches were driven south to their current range in Africa.