As we rattle across the moonscape towards the lost Kingdom of Mustang, the jeep's rear window falls out. One of the passengers, a middle-aged Indian man, with a dusty holdall jammed between his knees and chest, kindly raises the alarm. We screech to a halt and begin weaving back up the track in reverse at a similar breakneck speed until we find the mislaid window. Miraculously, it is in one piece - which is more than can be said for my sanity.
Mustang is Nepal's "Tibet" - a remote and beautiful region of ice-topped Himalayan peaks, wind-carved black and red cliffs and rustic villages of stone, clay and timber. We are lurching up a new road, the teenage driver keeping time to the Hindi techno blasting from the jeep's speakers.
The road has changed the face of Mustang, previously only accessible by hardy trekkers, mule caravans or helicopter. Now, creaking trucks carrying supplies and white jeeps, like ours, ferrying Hindu devotees from Kathmandu and India ply the route from Jomsom (the district's capital) up to the border with China.
An hour-and-a-half later and we are in Muktinath - or, more accurately, the Wild West one-road town of Ranipauwa. A small one-monk monastery, a police post, what looks like a dental surgery, with a toothy smile for a sign, and more than a dozen guesthouses make up Ranipauwa. It is ringed by snow-capped peaks that are at their most magnificent in the morning, when the sky is clear and the dawn glow paints the summits butter yellow. The monster is Dhaulagiri, meaning "dazzling mountain", and, at 8,167 metres, it is the world's seventh highest.
For the Hindu devotees, though, the mountains are just icing on the cake. They've come for the Muktinath Temple - a small shrine to the god Vishnu. Here, men, like happy seals, strip down to their underwear, posing for photos in the temple's sacred shower, water droplets glistening off rounded bellies. Despite the temple's small size, it is very important for both Hindus and Buddhists.
At the equally tiny Jwalamai Temple (tended by 30 Buddhist nuns), behind an unprepossessing pile of stones, are the three eternal flames - one in soil, one in water and one in rock, as a hotel owner in town explains. "But the one in the rock's gone out," he adds. A Himalayan youth with almond eyes grabs a torch and points out the remaining flames, two licks of blue flickering a hand's span from a sheen of flowing water.
"It's a miracle," he gasps.
Indian sadhus, or holy men, congregate at the complex's entrance. There are a couple of naga (naked sadhus caked in ash). One is bouncing up and down on a stick placed horizontally between two stones and onto which he has wound his penis like a spring.
"Look! Look!" he shouts gleefully, pointing at his crotch with both hands.
Behind me, a clothed sadhu is too busy texting to offer moral support.
In town, I meet Tek Bahadur Gurung, a 47-year-old conservation officer who has been dispensing advice to trekkers and helping villages in Mustang for 14 years. His skin is crisped red by the sun; the heat literally burns at this altitude. He says trekkers hate the new road as they now have to battle clouds of dust from the traffic. For the villagers, however, the road has made life easier: from Jomsom it used to cost 17 Nepalese rupees (HK$1.30) for every kilo to be transported by mule; nowadays trucks transport the same amount for seven to eight rupees. Jeeps also ferry crowds of Indian pilgrims, but Gurung is dismissive of their contribution to the local economy.
"They don't even stop for so much as a cup of tea," he complains. They stay in Jomsom, jeep to the temple, bring their own picnic supplies, and then jeep back in the afternoon, he says.
I find his words a little harsh, as I have spotted several Indian visitors haggling over the silver-black ammonite fossils (sacred to Hindus) that are sold all over town on street-side souvenir stalls.
Muktinath is a marvellous place to wander around. There are medieval villages, monasteries lodged on outcrops and, wherever you look, mountains. The people up here call themselves Himalayan - they practice Tibetan Buddhism, the women dress in Tibetan clothing (wrap-around chubas and striped aprons) and they speak a language close to Tibetan. A Free Tibet flag flaps from the spire of a guesthouse.
From here it's half a day's trek to the Thorong Pass (5,416 metres) - part of the famous Annapurna circuit - or a four-hour descent past swaying barley fields and striated stony cliffs to Kagbeni (2,820 metres), the gateway to Upper Mustang.
Kagbeni is a web of twisted alleyways, tilting stone walls and homes that resemble crumbling castles with turrets, peepholes and wooden doorways, some padlocked, some swinging open to reveal straw-filled pens of chickens, horses and even a snorting bull.
Around one bend is a line of prayer wheels groaning, thirsty for oil; another opens on to a courtyard with a communal tap. Behind one archway is a crudely carved stone man, left hand on his chest, right hand clutching a dagger. Emerging from his striped skirts is a lifelike phallus, protruding at an impressive 90 degrees. He is a kheni, or eater of ghosts, and he protects the village.
In contrast to the surrounding desert of rock, the village's farmland is neatly terraced and irrigated to support fields of barley, buckwheat, maize and vegetables, and orchards of apples and apricots. Kagbeni lies on the ancient Salt Road, between Nepal and Tibet, so-called because rice from Nepal's lower plains was exchanged for salt from the plateau's dry lakes.
Today, it is a town of two faces - the villagers have hosted trekkers for decades and guesthouses merge seamlessly with family farms. Children play hopscotch on a sun-dappled stretch of courtyard, North Face-clad tourists peep round corners snapping photos, while a calf with camel-long eyelashes wanders the alleyways looking for its mother. During the day the adult cattle are herded out to pasture, while the young are let loose in the warren of alleyways.
This is a Tibetan village, and spiritual guidance is provided by the 600-year-old Kag Chode Thupten Samphel Ling monastery, home to about 30 young student monks who swarm up and down the stairs in a blur of maroon. They carry battered copies of Nepali textbooks and kick their plastic sandals at each other.
At the border with Upper Mustang, unmarked except for a politely worded reminder in English to obtain a trek-king permit, is one of the world's most remote cafes. Applebee's not only serves what appears to be genuine Illy coffee but has a terrace perched on the edge of a cliff - the mighty Kali Gandaki River rolls below, while the forbidden track on the right snakes invitingly north. As dusk approaches, a sea of goats flows past, heading back into town. Indeed, more goats than people probably pass this cafe.
The solitude affords the perfect setting to ponder something a sadhu had told me earlier. The orange-clad septuagenarian, who spoke excellent English, said he had his own library and laboratory back in Kathmandu. After 40 years of being an ascetic he was now enlightened "a bit". He offered this piece of wisdom: "Time," he said, "is God's mind."
Getting there: Nepal Airlines flies three times a week from Hong Kong to Kathmandu. From the Nepalese capital there are more than a dozen daily flights to Pokhara (30 minutes) and another five or six a day onwards to Jomsom (20 minutes). From there either hike (half a day) or jump in a jeep to Mustang.