Before dawn the temperature in the Sahara falls to close to zero in the early winter months. In January and February it drops below. You soon learn the art of crawling out of your sleeping bag while speedily putting on as many layers of clothing as possible in the dark without falling over into the damp sand. By 7am, however, you can already feel the heat of the sun and by 8am it is pleasantly warm. From then on you shed layers like an onion as the temperature steadily rises.
The Great Eastern Erg cuts a vast, sandy arc across Algeria and Tunisia, touching Libya. It is one of the largest of the ergs, which mean "vein" in Arabic. There are five main veins coursing through this vast desert expanse of north Africa. Such uncompromising lands of stark beauty and solitude have become second home to Jean Louis Bernezat and his wife Odette. For nearly 30 years they have been criss-crossing the deserts of Africa, developing a specialised tour business.
In small, French-speaking groups you can go trekking during the winter months from October to April (the summer being too hot) in Morocco, Tunisia, Mauritania, Namibia (all year round) and, for the first time this year, Libya. The tours range from one-week trips to serious, five-week, Lawrence- of-Arabia stuff.
These are holidays for those who like to rough it and enjoy a reasonable physical challenge. My wife and I opted for one of the shorter trips - 11 days including seven days trekking - in Tunisia's Great Eastern Erg. Though reasonably sporty, neither of us is a serious walker. Of the other six in our group, most were keen ramblers.
The trek proper began once we were deposited near the edge of the Erg at a dried-up well called Bir Abdallah. Eight camels were waiting for us,accompanied by their owners, Mustapha and Msbah. The world of casual tourism was left well behind during our boneshaking ride south by Land Rover from Tozeur. All lingering thoughts of the luscious date plantations we had jolted past were blanketed out by the heat, dust and the sheer emptiness of where we made our first bivouac. We slept that night, as we would every night, in the open.
The following morning, after only a couple of hours' walking, we reached the Erg. It was as if some Olympian landscaper had cut a carefully delineated border, as the flat, scrawny scrubland ceased, and the undulating, sandy vastness began. A day later we reached Tumbain, a flat table mountain from whose top you look out on the infinity of the erg. The solitude of the place was awesome.
It is not the custom here to ride on camels. They carried all our supplies while we walked, though should anyone have fallen ill, they were there as an emergency ride. Serious medical help, however, would have been days away.
Our life soon fell into a pattern. Up just before dawn, a quick breakfast before loading the camels, and then a good four hours' walking. The sand is surprisingly firm underfoot. Sometimes we followed the caravan as it took the route of least resistance, but mostly we meandered across the crest of the high dunes, pursuing the diminutive figure of Ibrahim, swathed in his black shesh, as he padded bare-footed to the rhythm of his staff and his own thoughts. One imagines the landscape to be monotonous, but it is not. The play of light in the mornings and evenings, the sheer immensity of the place, the artistry of the dunes, some over 100m high, with their amazingly clean lines and graceful forms, are constant sources of wonderment.
Some time after 11am Ibrahim would plant his staff in the sand and we would all slump to the ground with an angry buzzing of hundreds of suddenly disturbed flies. The midday meal was a salad of cabbage, onions, olives and sliced lemon that tasted as if it was made by the angels. It came, as did everything, with a soupcon of fine-grained sand.
In the afternoon, we would walk for another two hours or more before finding a spot for the night and beginning the evening rituals of unloading the caravan and gathering firewood. Around the camp fire, Msbah would sing while Mustapha blew and grunted into a hand-made flute that looked suspiciously like the piece of plumbing missing from under the sink at the hotel in Tozeur. There followed much drinking of strong, sweet tea brewed in a battered metal teapot bubbling on the embers. Exhausted by the day's walking, we were usually all in our bags well before 9pm, gazing up at the wide-screen entertainment of the desert night sky, emblazoned with the Milky Way and the nervous flashes of shooting stars. The moon rose late, and shone with such intensity as it became fuller that you would waken during the night to a floodlit landscape bright enough to read by.
Most nights I was lulled to sleep by one of the camels, which, having found a flavoursome bush next to my sleeping bag, would treat me to a stereophonic display of its digestive rhythms. In the morning, the dew- soaked sand opened like a book, recounting the activities of the night that had gone on around us as we slept. There were the scratchy trails of beetles and lizards, the claw marks of kangaroo rats and desert mice, the dragged belly lines of a hedgehog and the energetic side-swipes of a viper.
It was from atop a dune of alpine proportions that we first saw Lakhwazat lake, the high point of our trip. Curling across a depression in the middle of the dunes, the silvery stain of the water seemed incongruous after four days of the nothingness of parched sand and heat. Ducks played among the reeds, and a few wild donkeys wandered about. The water flowed into the lake from a spring that bubbled up in the middle of the sand. The pungent, sulphurous water emerged, the temperature of a warm bath, into a small, natural, sandy tub. The aches from days of hard slogging slipped away as I lay in this heavenly pool. Only the sound of bubbling water broke the peace. I knew then that I had discovered the finest jacuzzi in the world.
John Eisenhammer bought his trek through Hommes et Montagnes, 38500 Voiron, France (00334 76 66 14 43)