Is this the perfect desert town?

The inner walls, which glowed white with a protective layer of limewash, were made of sun-dried mud bricks. This mixture of clay, sand and straw was layered above stones that insulated them from moisture. Dr Susannah Hagan, emeritus professor of architecture at the University of Westminster and an expert on green architecture, later explained why this building technique is so ingenious: “The secret is in the walls: thick walls of earth or stone that delay the sun’s heat penetrating a building interior during the day, and radiate that heat back to the cold sky at night,” she said. “By morning, the walls have cooled enough to start the protective cycle again.”

She added: “Skilful use of available building materials [achieves] the maximum comfort with minimal means. In the desert, this means coolness without air conditioning, and warmth without heating.”

Continuing, we passed doors of simple palm trunks, some studded with brass, as well as low arches, curved alcoves, and dakkar – built-in benches – which, perfect for lounging, usually indicate a nearby mosque (there are 21 of them, though only a handful are still in use, and only on Fridays). Sometimes the arches were incised, chiselled or decorated with delicate paintings (a hand of Fatima, a star, intricate geometries), adding to the mystery and allure.

At the hub of the medina, we arrived at two arcaded squares enclosing giant mulberry trees. This, Manshour said, was where slave markets were once held. Indeed, it was this centuries-long trade of sub-Saharan men, women and children that, shamefully, spurred the economic heyday of the town ­­– and ultimately brought its downfall once the practice was abolished in the 19th Century.

But long before its demise, this caravan crossroads had flourished spectacularly as a hub of itinerant traders swapping exotic goods such as ostrich feathers, gold, ivory, civet, brass and pewter as well as weapons and horses. Ghadames is strategically located where Tunisia, Algeria and Libya today meet, and it was from here that the loaded camels would plod onwards west to Timbuktu, south to Ghat and Bornu or north to the Mediterranean ports. The town became a key meeting point of civilisations, and its Berber (known locally as Amazigh) inhabitants, the Ghadamisa, were much revered.

Thus it flourished until the abolition of slavery, nominally bowing to Ottoman rule and with interludes of Italian and French occupation in the early 20th Century. In the 1980s, a shortage of water and lack of modern sanitation led Muammar Gaddafi to order the building of a new town next door.

Today, Old Ghadames has no permanent residents, although during the sizzling summer, its environmental superiority compared to the concrete apartment blocks of the new town lures a steady trickle of Amazigh and sub-Saharan locals, who return to enter its mosques and tea-rooms and relish its cool beauty.

They also come to tend many of the 121 family gardens, which are irrigated by a complex system of channels from artesian wells and the underground Ain al-Faras spring – the legendary origin of the oasis. Sheltering beside the gardens in the shade of date palms and fruit trees, I admired the town’s crenelated external walls. The natural ochre hue from the mud bricks was edged in white, surmounted by triangular openings and extravagant finials, both typical of Saharan architecture across the Maghreb. Manshour laughingly told me that the pointed finials are to prevent djinn (malicious spirits) from landing on the rooftops.

Back in the cool maze, we entered one of the few private houses open to the public. From ground-level storerooms, stairs rose to the tamanhat (living room). It was a revelation. Compared to the white minimalism of the streets below, here was an explosion of riotous colour, texture and decoration: geometric wall paintings in brilliant scarlet, sumptuously patterned cushions and rugs, cupboards and niches containing dusty family memorabilia and dozens of wall-hung copper pots and mirrors, both designed to refract available light. This multiplied when Manshour opened a trapdoor in the ceiling, unleashing a flood of sunbeams.

At the very top of the house, beyond a rudimentary kitchen and shaded patio, a last flight of steps led to a large roof terrace and yet another architectural eye-opener: an astounding jigsaw of low parapets, finials, steps and walkways connecting each home to its neighbour and ever onwards across the medina.

This elevated world, Mansour explained, was the domain of the women who, limited to using only one main street below as per local Islamic custom, would spend their days cooking, sewing and socialising while acting as lookouts for approaching caravans. Some would even sleep there during the hot summer nights.

As the merciless sun beat down on this luminous white geometry rimmed by tufted green palms, it seemed patently clear that the best deal was reserved for the men in their cool, shadowy underworld. But what both men and women shared was the beauty, intelligence and complexity of this remarkable abandoned town, lost in the depths of the Sahara, yet still enjoyed – intermittently – today.

Heritage Architecture is a BBC Travel series that explores the world’s most interesting and unusual buildings that define a place through aesthetic beauty and inventive ways of adapting to local environments.

—

Join more than three million BBC Travel fans by liking us on Facebook, or follow us on Twitter and Instagram.

If you liked this story, sign up for the weekly bbc.com features newsletter called “The Essential List”. A handpicked selection of stories from BBC Future, Culture, Worklife and Travel, delivered to your inbox every Friday.