On the grandaddy of rafting journeys, you can imagine dusty, wagon-sick pioneers taking to the water - less "wagons roll!", more "rafts afloat" - to head west. This is not just about crazy rapid-running, but a complete journey through the biggest chasm in the earth's surface that's not currently filled by an ocean. Of course there is quite a bit of water at the bottom - sometimes tranquil, sometimes raging - providing a unique perspective on Arizona's Grand Canyon along its entire length. From the Lee's Ferry starting point it's 225 miles and up to two weeks to the finish at Diamond Creek but you'll cover many more miles on daily hikes around the canyon. There are plenty of rapids throughout the trip, though the breathtaking geology, from vast riverside caves to the technicolour canyon walls, followed by incomparable night skies, may leave an even deeper impression.
When to go: May to October
Canyon Explorations Expeditions (00 1 928 774 4559; www.canyonexplorations.com)
The White Nile, Uganda
If you're short of time to spend on water, you can still have the full rafting experience on the White Nile near Jinja in Uganda, taking in several grade-five rapids in just a couple of days. At its source, the White Nile has some of the most ferocious big water rafting on earth. Down-time between rapids is equally impressive, with stunning bird-life to admire as you drift between densely forested islands. But the news that you can swim in some of the calmer stretches may not impress you after seeing the number of hippos that like to do the same.
When to go: year round
Rainbow Tours (020-7226 1004; www.rainbowtours.co.uk)
Coruh River, Turkey
High in the Kackar Mountains in the remote north-east of Turkey, a younger, wilder cousin of the biblical Euphrates rises: the Coruh. Spring is the time for white water, when the rapids, fed by meltwaters, grow to grade five. In its 155-mile journey to the Black Sea coast at Batumi in Georgia, the river cuts through canyons, narrow valleys of orchards and paddy fields, and passes ancient ruined castles. Civilisation, though it originated not far from here, manages only a tenuous toehold, making it all the better to be travelling self-contained, by raft, spending each night at remote riverside campsites.
When to go: May to July
Adrift (01488 71152; www.adrift.co.uk)
Futaleufu River, Chile
With river grades that go as high as the commercial rafting scale allows for, you might think a Chilean rafting trip is simply about the biggest white water. That's certainly part of the experience, but there's at least as much off the water too. The Futaleufu emerges from Argentina, cutting between the massive peaks of the Andes and into northern Patagonia. The water, when it's not foamy-white, is a miraculous, clear azure and the views range from glacial peaks to lush forested foothills. The rapids build along the route until, a week into the ride, you're ready for grade five. If not, you can always walk, and the route includes a couple of mandatory "portages" which circumvent sections where no-one runs the river regardless of how fearless they're feeling. Time off the water is pretty full-on too, with mountain biking, horse-riding, hiking, fishing and starlit barbeques to end each day.
When to go: January to March
Momentum River Expeditions (00 1 541 512 2727; www.momentumriverexpeditions.com)
Tamur River, Nepal
Big mountains make powerful rivers so it follows that one of the world's supreme rafting trips is within sight of Everest, Kanchenjunga and Makalu - the first, third and fifth highest mountains on earth. Just reaching the Tamur river involves an adventurous trek through the east of Nepal, where the concept of flat simply doesn't exist. Vast teams of porters lug the gear so that you can enjoy the tranquil rhododendron forests, sunny meadows, rice fields and startling views as you prepare yourself for a ride which can't fail to impress. At least as irresistible and infinitely more charming than the surging waters, are the locals, for whom your visit to their villages and homes is as much an honour as a business opportunity.
When to go: September and October
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