It's not often something stops you in your tracks, makes you pull the car over, get out and stand there, gawping. But then I had never seen a tepui before. Let alone thought about climbing one.

In the far southeast of Venezuela, the grasslands of La Gran Sabana stretch across an area the size of Belgium, accessed by only one road and home to the Pemón people. The Angel Falls tumble 979m (3,212ft) to earth from one tepui, making it the world’s tallest waterfall. And across the landscape, rising almost mythically out of early morning mists, are more of the huge, flat-topped table mountains, the tallest of which, Roraima, inspired Sir Arthur Conan Doyle to write The Lost World.

These mountains are the remnants of a thick layer of sediment laid down two billion years ago when the Americas and Africa were one land mass. Over time erosion left behind only the more resilient rock structures and now the 25 or so main tepuis have a wealth of endemic flora and fauna – frogs that don’t hop and bypass the tadpole stage, and small, red carnivorous plants, for example.

From a distance, Roraima’s sheer 800m rock walls, poking up from a layer of dense forest, make it look impossible to scale, but in 1884 the British explorer Everard Ferdinand Im Thurn discovered a thickly wooded natural ramp up the side and scaled its peak. Now I was to follow in his footsteps accompanied by my local guide, Ricardo Brassington, and Pemón porters carrying tents and cooking gear for the five-day trek.

The first two days were gentle walks across open grassland, occasionally fording rivers, on the lookout for armadillos and giant anteaters, avoiding hairy caterpillars the length of a finger, angry-looking ants the size of a thumbnail and (more difficult to escape) the puri puri sand flies, which must rank among the world’s most devious, sneaky and impervious to insect repellent. In the evenings Ricardo whipped up dishes inspired by his childhood in nearby Guyana – “cook up” (rice and peas) and curries.

The four-hour assault on the top came on the third day – a sweaty, tiring, fascinating scramble up steep paths, along streams, over boulders and around thick tree trunks. From ground level we passed through cloud forest and under waterfalls until we emerged on the lunar landscape of the summit, looking towards the neighbouring and equally majestic tepui of Kukenán.

“This is my 55th climb up Roraima,” Ricardo said, “but each time I feel like it’s my first. Each time is amazing.”

I looked around, but initially found it difficult to share his enthusiasm. The tepuis create their own micro-climates, and cloud and mist swirled around me. I was cold, wet and exhausted.

“Let’s explore,” said Ricardo enthusiastically. I sat shivering in my tent, clutching a hot chocolate laced with rum, and tried to find some clothes in my backpack that weren’t soaking wet. “Let’s see if the weather improves,” I replied, less enthusiastically, retreating to the depths of my sleeping bag, before spending a cold night feeling rather sorry for myself.

But the next morning was a stunning revelation. I unzipped the fly-sheet and poked my head out, expecting to be faced with more depressing fog. Instead the sun was already high in the sky, illuminating a scene that would surely have justified Conan Doyle’s wild imagination. With Ricardo and one of the porters, I explored for several hours away from camp, like a small child continually fascinated by new discoveries; along sandy paths to small pools of water and the little black frogs that lurked within; gleaming quartz rocks (there are diamonds up here, too); spiky tufts of grass and stumpy, wind-gnarled trees. Mist covered us at a moment’s notice, then blew away as quickly as it came – not the most comforting sensation with sheer drops near by.

The luxurious feeling of solitude was immense and overwhelming. In the far distance we could faintly hear the voices of some Venezuelan students, but other than that we were alone. It really was a lost world.

The climb down later that day was tougher than the ascent. But the valley floor was a welcome return to warmth. At the campsite we celebrated with rum and passionfruit juice and I chatted to two Australians who were on a five-month expedition across the continent and had also descended from Roraima.

“It’s one of the most special places we’ve seen so far in South America. The landscape and plant life up there are awesome,” said Matthew Rafty, from Perth.

After our two-day walk back to the base village of Paraitepui, Ricardo and I sat in a small café eating grilled chicken, watching the Venezuelan president, Hugo Chávez, on television greeting his Iranian pal Mahmoud Ahmadinejad in Caracas. President Bush appeared saying goodness-knows-what in dubbed Spanish, although I understood the word “Iraq”. Pictures showed marchers being shot on the streets of Rangoon. Roraima isn’t just a haven for small black frogs and insect-eating plants. It’s also a brief, beautiful refuge of sanity for those looking to hit the pause button in our rather shabby modern world.

Need to know

Will Hide travelled with Geodyssey (020-7281 7788, www.geodyssey.co.uk), which offers individual and group trips to Venezuela. A 12-night Trek to the Lost World to climb Mount Roraima and then travel by dugout canoe to Angel Falls, is from £1,225pp, including most meals, but not international flights.

Air France (0870 1424343, www.airfrance.co.uk) flies to Caracas via Paris from Heathrow and seven regional airports, from £456 return.

Further information: Roraima can be climbed year round, but the driest period is between October and April. Latin American Travel Association (www.lata.org).

Walk this way...
Will Hide

Argentina
Last Frontiers (01296 653000, www.lastfrontiers.com) organises hiking in the Fitzroy National Park as part of a nine-day trip in Argentina. From £1,865pp, including flights and some meals.

Bolivia
KE Adventure Travel (017687 73966, www.keadventure.com) has a 20-day “traverse of the Cordillera Real” holiday in Bolivia, which crosses three 5,000m passes. From £1,195pp, including some meals, but not flights.

Chile
An eight-day trek in the Torres del Paine National Park, circumnavigating the torres (towers) and cuernos (horns) is offered by Journey Latin America (020-8747 8315, www.journeylatinamerica.co.uk). From £1,821pp, including flights and meals.

Peru
Headwater (01606 720033, www.headwater.com) is introducing a Peru holiday next year that takes in the main Inca highlights. From £2,999pp, including flights and meals.

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