On the horizon a massive stone city the color of earth through a haze of blowing sands seems to rise up out of the desert itself. As the distance between us closes I can see its towers crumbling into an otherworldy landscape of ruin. Ouadane, on the southern edge of the Adrar Plateau in Mauritania, had once been a staging post in the trans-Saharan trade and a stop for caravans transporting slabs of salt from the mines at Idjil. Now its remains are protected as a UNESCO World Heritage Site.

Part of the city is more or less intact, and another part has been restored, but there is still a large section that remains a massive pile of rubble. Ouadane was a typical Ksar, a walled city construction style common in the Sahara, and though the walls have fallen into ruin, I still must enter via a gate — a very modern chainlink style fence — opened by a kind caretaker who keeps a watchful eye over the lonely outpost, protecting this precious cultural resource from vandalism or looting.

Ouadane was founded in 1141 on the ruins of four cities, themselves created in 742. Details from the earliest history are uncertain but the town prospered from the trans-Saharan gold trade during the time of the Ghana Empire. In the middle of the 11th century, the Arabic geographer al-Bakri described a route that ran between Tamdoult near Akka in Morocco to Aoudaghost on the southern edge of the Sahara that passed this way. One of the first written references to the town by Gomes Eanes de Zurara described Ouadane as the most important town of the Adrar region and the only one with a surrounding wall. Fifty years later Valentim Fernandes wrote a detailed account of the trade in slabs of salt from the Idjil mines and the role of Ouadane as an entrepôt. Estimates in accounts from 1505-1508 put the population somewhere between 400 and 1,800 inhabitants.

Exploring the ruins is like delving into a mystery. Dark shadows alternately hide and reveal details as I pass through the old alleyways weaving between a hodgepodge of half crumbled houses and scattered stones. Bits of remarkably intact buildings cling desperately to the cliff face in defiance of time. The wind picks up some fine sand, swirling it into an ever rising column of dust that then disappears behind the rubble into thin air, seeming very much like a ghost or a spirit.

It’s hard to believe that there was once a bustling cosmopolitan city in this remote corner of desert, but Ouadane is truly awe-inspiring, an ancient city so much larger than any of the little towns I passed through on the multi-day journey to reach it. It’s continued presence is a testament to the once great system of caravans that carried things and knowledge across the vastness of the Sahara, spreading culture and wealth throughout an area that today seems to struggle just to eke out a subsistence living.

The name “Ouadane” means “the city of the two wadis” — the wadi of knowledge and the wadi of dates — and the city experienced an intense spiritual radiance during its period of prosperity, becoming a focal point of Islamic culture in addition to a trading and religious center. The first university in the desert came into being here and many ancient Koranic scholars acquired their knowledge by studying in Ouadane — in fact, the oldest manuscript found in Mauritania was discovered here (it is now in the national library in Nouakchott).

The city was once so important that the Moroccans targeted it in multiple attempts to take control of the trans-Saharan trade in salt and gold, organizing military expeditions to occupy Ouadane in 1543-44 and again in 1584, which eventually led to the collapse of the Songhay Empire in Sudan.

The salt caravans continued, even after the transport of gold and slaves ended. But slowly the population began to leave due to increasingly difficult living conditions caused by the growing aridity of the climate. Ouadane experienced its final decline at the beginning of the 20th century when the camel caravans were replaced by modern mechanized transport and the slow exodus of the last remaining population continued into the 1960s. The city itself was left to erosion and the wind.

Startled by the sound of movement coming from the rubble, I turn to see a small desert marmot scrambling out of the rock pile, one of many wild animals who have made a home here in the absence of humans. The little fellow quickly moves out of sight, and I continue exploring Tegherbeyat, the upper ruined section of the town, which is almost certainly the oldest. There would have been a mosque somewhere here, but no traces of it have survived. Many of the structures in the ksar that have not already crumbled to the ground are in a precarious state of disrepair. Protecting and preserving what is left was a key impetus for obtaining UNESCO World Heritage status.

Inscribed as a UNESCO World Heritage Site in 1996, the medieval ksar of Ouadane highlights a traditional way of life among the nomadic cultures of the Sahara, with a unique “security”-focused urban morphology of narrow winding lanes leading upward and protected inside high walls. The houses are built around central courtyards and densely-packed close to the mosque. Saharan ksars are particularly well designed for the extreme climatic conditions of the desert, both as regards construction methods and the occupation of space.

Walking through narrow labyrinth-like streets that twist and turn as they climb can be confusing, and I am thankful for a restored minaret that serves as a navigational waypoint. This very atypical minaret is neither tall nor narrow, instead it is square and somewhat reminiscent of a turret built for military purposes. Part of the single remaining mosque in Ouadane it received some modern restoration attention without detracting from its ancient charm. The mosque was built in the 15th century as the town expanded, and the remains of clay plaster on some walls suggest that it was abandoned in the 19th century.

The mosque is one of several structures that have benefited from restoration efforts, and it is nice to see how modern and ancient blend harmoniously without really defining a boundary between the two. Continuing towards the top of the city assemblage I somehow find my way to the edge of the outer wall and stepping out of the cool shadows of the narrow alleyway, I can suddenly see the entire vastness of the desert stretching out towards the distant dunes that creep ever closer, still threatening Ouadane’s existence.

Accessing the protected site at Oudane is easy once you manage to reach it, but the journey there requires a multi-day route across sandy desert tracks. The site is administered by the Mauritanian government under Law 46-2005 concerning the protection of tangible cultural heritage. The Ministry for Culture is the authority responsible for the enforcement of the laws concerning the protection of cultural properties. The Directorate of Cultural Heritage ensures that standards are being observed and is carrying out an inventory of the cultural properties in these towns.