Vast stacks of sandstone loom over the arid valley of Wadi Musa like giant handfuls of sun-baked clay. But even in this parched landscape, there are places where the sun casts no light. Walls 200 metres high keep the Siq permanently cast in shadow – it’s as though the long, narrow canyon passes through the dark heart of the mountain itself. Utterly silent at dawn, there is not even a bird’s chirrup to accompany solitary footsteps along its patchwork floor of rock and sand. Soon, the senses adjust to their deprivation – the plodding becomes rhythmic, the soundlessness ordinary. Occasionally there’s a clue of what’s to come: a lone fig tree, fragments of ceramic pipes which once channelled water, a relief carving of a camel caravan – so weathered that only hooves and feet remain.

After half an hour, through a lightning-bolt shaped opening, Petra announces itself with deliberate drama. The vast façade of the Treasury, precisely carved into the soft sandstone, towers over the young Bedouin men, camels and stray cats that congregate at its base. ‘[Its] situation and beauty… are calculated to make an extraordinary impression on the traveller, after having traversed… such a gloomy and almost subterranean passage,’ the Swiss explorer Jean Louis Burckhardt wrote in his diary in 1812. ‘It is one of the most elegant remains of antiquity existing.’

When Burckhardt crossed Petra’s threshold, he was the first outsider to do so for over 600 years – hidden by its natural fortifications, the city had remained obscure to the West since the time of the Crusades. Though known to local Bedouin tribes, they were reluctant to reveal its existence, justifiably fearing an influx of treasure hunters. In Petra’s heyday, around the time of Christ, the city had been anything but anonymous. Home to some 30,000 people, whose survival in this desert landscape was maintained by a complex system of water management, it was the centre of a kingdom four times the size of modern Jordan. At its helm were the Nabataeans, a oncenomadic Arab tribe who had used their knowledge of the desert to amass vast wealth in the caravan trade, most lucratively that of frankincense and myrrh.

The Treasury’s grand edifice was a statement of their wealth, sending a powerful message to weary traders emerging through the Siq, but was essentially an empty shell. Built as a tomb for a Nabataean king, its misnomer ‘the Treasury’ came from the belief that the urn carved into the centre of the second tier contained hidden gold. The vessel is pockmarked with bullet holes, evidence of past attempts to uncover the mythical bounty. ‘The idea of treasures being hidden in ancient edifices is strongly rooted in the minds of Arabs and Turks,’ wrote Burckhardt in his diary. ‘They believe that it is sufficient for a true magician to have seen and observed the spot where treasures are hidden in order to be able afterwards... to set the whole before him.’ An Arabic expression meaning ‘He has indications of treasure within him’ was something he became sick and tired of hearing.

The treasure Burckhardt sought was intellectual rather than mercenary, and his visit to Petra was the result of years of careful academic preparation. In 1809, as part of his work with a British association hoping to discover the source of Africa’s Niger River, he moved to Aleppo in Syria. He mastered Arabic, converted to Islam and took the name Sheikh Ibrahim bin Abdullah. A deep tan and full beard further obscured the 27-year-old’s ethnicity, and he became a master of disguise, adopting local customs and testing his alias among the Bedouin. When, travelling south to Cairo, he heard rumour of ruins hidden among the mountains of Wadi Musa, he was quick to devise a ruse: ‘I pretended to have made a vow to have slaughtered a goat in honour of Haroun (Aaron), whose tomb I knew was situated in the extremity of the valley,’ he wrote, ‘and by this stratagem I thought that I should have the means of seeing the valley on the way to the tomb.’

His plan worked. Upon entering the city he was barely able to conceal his wonder from his guide. As the two made their way deeper into the valley, Burckhardt was gobsmacked by the sight of countless tombs and the great amphitheatre carved into the rock. He couldn’t resist scrambling up to explore. Then, as now, these caves were utterly bare; unadorned but for the veins of colour striped through the rock like a sort of natural wallpaper. Having surprised his guide with his incursions, Burckhardt was hurried to the city’s parched core, the Colonnaded Street and the temple of Qasr al-Bint. His attempt to wander the ruins of the latter was the final straw. ‘I see now clearly that you are an infidel!’ his guide exclaimed. ‘But depend upon it that we shall not suffer you to take out a single [one] of all the treasures hidden therein!’ Fearing that further aggravation might lead to the discovery of his own most treasured possession, his diary, Burckhardt dared venture no further. After a few stolen hours, his exploration of Petra was over.

Others have spent a lifetime navigating the city. 27-year-old Laith Odah was born in one of the caves carved into the mountains behind the Theatre. He and his ten siblings spent their childhood among the ruins, playing football and a Bedouin game not unlike pick-up-sticks. ‘It was a good place to grow up,’ he tells me over sweet, spiced tea, served in dainty glasses. But he wasn’t sorry to leave when, in 1985, the Jordanian government decided to re-house Petra’s Bedouin families away from the most significant Nabataean monuments, in a purpose-built village behind the archaeological site. ‘Living in a cave, it wasn’t easy,’ he says, smiling broadly. Still, Laith spends every day in Petra. Until recently he earned a living offering tourists the services of his donkey, Casanova. ‘He was strong, could carry four people at once, but he got sick. I nursed him for days, feeding him camel’s milk, but he died.’ With two fingers, Laith traces tears from his kohl-lined eyes. Until he can afford a new animal – a donkey costs between 200 and 400 Jordanian dinar (between £175 and £350) – Laith works as a guide. Today, in his keffiyeh scarf and Arabic robe, known as a desh dash, he’s to lead the way to Haroun’s Terrace: the last stop on Burckhardt’s all-too brief tour of Petra.

The steep climb in searing heat, is a good moment to make use of one the city’s many beasts of burden. Young men handling donkeys, mules, horses and camels pace Petra’s ancient streets from dawn until dusk, exalting the benefits of an ‘air-conditioned taxi’ or ‘Bedouin Ferrari’. Camels have acquired a sort of exotic majesty among Petra’s visitors, but in Burckhardt’s time they were the Ford Fiesta of the Bedouin transport world – utterly unremarkable, and therefore the perfect choice for the incognito explorer. My steed’s long legs pick their way through the archaeological rubble that surrounds Qasr al-Bint – fragments of Hellenic columns, lined up like slices of salami, and the bricks that once made up its walls. Few tourists venture beyond Petra’s main sites, and with every hoof-step away from the city we are more alone – until there isn’t a single other person in sight.

If the stretch from the Treasury to Qasr al-Bint is Petra’s high street, these outlying hills are the city’s suburbs. Though the weather-worn rockface is still peppered with ancient dwellings and sepulchres, many are more modest. Some grander efforts lie unfinished – vestiges of an urban sprawl that came to an abrupt halt – and with these edifices it is possible to see the Nabataean technique of carving from top to bottom. Ascending further into the hills, we come across what must be one of the last tombs still used as a Bedouin family home. Small but ornate, its dark entranceway has been filled with a solid door, and there’s a garden of plants and fruit trees. With the sun directly above us in the sky, we reach Haroun’s Terrace. From here, a small white mosque is visible. This is Jebel Haroun, thought to be biblical Mount Hor, where Moses’ brother Aaron (Haroun to Muslims) is buried – a sacred place for both Christians and Muslims. Burckhardt, arriving here at sunset, realised it was too late to reach the tomb and sacrificed his goat on the spot with a few hasty incantations. The sounds here today are gentler – the wind whistling across the desolate plain, and the clanking bells of a whole herd of goats, which I follow to a sheltered Bedouin camp.

A woman wearing a headscarf and long dress emerges from a rectangular tent covered in black cloth made from goat’s hair. She invites us in for coffee. Her home is cool in the midday heat, and she shows us into a room covered with woven carpets. On the wall hang posters of sites of Muslim pilgrimage – Mecca, and Al-Aqsa Mosque in Jerusalem – and strings of brightly-coloured tassels. We sit cross-legged on the floor as coffee beans roast in a pan over an open fire. Gasamah has eight children and the three youngest congregate on her lap to stare at the visitors. Two-yearold twins Mohamed and Amal occasionally stray to help themselves to cups of tea from a kettle that sits in the corner of the room. Gasamah’s home-life is typical of local families’, most of whom – like her – belong to the Bdoul tribe. Her husband has a donkey and a small souvenir stall in Petra, so she stays at home to look after the children, the 20 goats and a small garden sown with bamboo, apricots and grapes.

Though she clearly has little, Gasamah is happy to share with her guests. Hospitality is an important part of Bedouin culture, something Burckhardt relied upon heavily during his travels in the Middle East. An old Bedouin saying, ‘When a guest comes he’s a prince; when he leaves he’s a poet,’ shows not only the importance of a proper welcome, but the value placed on reputation – essential for survival in the desert. Though Gasamah admits that life here can be hard, she wouldn’t want to be anywhere else. ‘All our life is in this place,’ she says. ‘Here we are free.’

Like their Bedoui n descendants, the Nabataeans were originally a nomadic desert people, with no architectural heritage of their own. The style displayed in Petra was a hodgepodge of influences absorbed along their trading routes: Egyptian, Assyrian, Hellenistic, Mesopotamian and Roman imagery injected with their own creative flourishes. Nowhere is the scale of their ambition more apparent than at Petra’s biggest monument, the Monastery, carved deep into the mountainside. It is easy to imagine the hours of chiselling and carving that went into its creation. Even reaching the Monastery requires work – it sits at the top of an 800-step rock-cut path, following the route trod by the faithful when this was a place of worship. The Monastery’s name is misleading – built in the 3rd century BC as a tomb, it was probably later used as a temple. Crosses etched into the internal walls show that the Byzantines used it as a church – Petra is a place that has borne witness to the rise and fall of one civilisation after another.

In Indiana Jones and the Last Crusade, the fictional doctor’s quest for the Holy Grail led him to Petra. Dr Saad Twaissi, Dean of Archaeology at Petra’s Al-Hussein Bin Talal University, is the real deal, devoting his life to unravelling the mysteries of the site. ‘The first excavations of Petra were in 1929, and they have happened continuously since,’ he tells me in the perfect English he acquired during PhD studies in Bradford. ‘And yet still, we know little about the Nabataeans.’ With no surviving written sources, Petra’s built environment provides academics’ most valuable resource. ‘The great difference in the tombs tell us that it was a stratified society. From inscriptions inside them, we think that the average family size was five or six persons.’ The Nabataeans were polytheistic – with gods for fertility and trade, and so on – and believed that high places were sacred. It seems that women had a prominent role. ‘Women were always shown next to the king on the obverse of coins – this is rare, even in modern states, and was probably a consequence of their trading economy; with the men frequently away, women were left to organise society and consequently gained higher status.’

Saad’s particular interest is not in the grand façades that have made Petra famous, but the houses of the Nabataeans. ‘The rock-cut monuments are all tombs, or places of religious significance,’ he says. ‘Their homes, markets and temples were built with stone and therefore did not survive the seven earthquakes that destroyed so much of this place. The built city – the true city – still lives underground. I’d say only about five per cent of Petra is known to us now.’

Burckhardt saw only a fraction of that still – he didn’t even make it as far as the Monastery. Though a letter back to his colleagues reporting his discovery caused wild excitement, he never got to enjoy a moment of his fame. He lived out the rest of his life travelling the Middle East and Africa as Sheikh Ibrahim bin Abdullah, before dying from dysentery in 1817, at the age of just 32. In the two centuries that followed, countless others – explorers, scholars and the simply curious – have followed in his wake, but still Petra remains a place full of untold secrets.

The article 'Unveiling the secrets of Petra' was published in partnership with Lonely Planet Traveller.