Looking for adventure? Try a mountain bike ride down what is possibly the most dangerous road in the world -- the narrow track from high-altitude La Paz to the sultry jungles of the Yungas!

The Aymara women tending the bizarre stalls at the Witches Market in La Paz are not known for being friendly; and they will shoo away inquisitive tourists, especially those with cameras. But Josephina was different, and happy to explain the tricks of her superstitious trade. The dried llama foetus, placed in a bowl of pastel-shaded sugar candies and twists of wool, was an offering to ensure good fortune for a new building. The clay model of an owl was for intelligence, the tortoise for goodbyes; the condor was for safe travels, and this was the one I wanted. Facing a mountain bike ride down a road claimed to be the most dangerous in Bolivia, if not the world… I reckoned I needed all the protection I could get. I handed over a few coins and, clutching my talisman, tripped back down Sagarnaga St..

In a mountainous country where only 5 percent of the roads have any form of asphalt covering (with the result that the remaining ones frequently turn to mud with the onset of the rainy season), a road that is above all others in awfulness earns itself quite a reputation. Such is the road from La Paz to the Yungas, and in particular the unpaved, narrow section from Unduavi to the pit stop of Yolosa. Anyone who has ever travelled it will be in no doubt that the reputation is well deserved. This is a nerve-wracking route, with vertical drops of over 1 km (1/2 mile) off the side of a poor gravel track that takes you into impenetrable jungle. This so-called road is no wider than 3m (10 feet) in places, and passes under several waterfalls that further erode its already crumbling surface.

In a bus or car, the journey is thrilling enough, taking you down, via hairpin bends, 3,600m (11,800 feet) in altitude from snowy mountain peaks shrouded in clouds to sultry jungle. Riding on a mountain bike at speeds of up to 50 km (30 miles) per hour, and freewheeling past seemingly suicidal truck drivers and howling dogs, it's nothing short of an adrenaline injection straight to the heart. "You can't do rides like these at home," boasts the publicity leaflet for Gravity Assisted Mountain Biking, run by young New Zealander Alistair Matthew. This is no hype. The 64-km (38.5 mile) ride, which takes between four and five hours depending on the weather, will leave me exhausted, filthy and, Alistair assured me, exhilarated. I just hoped I'd be alive to tell the tale.

A Prayer for the Travellers

The only difference between the minibus that pulled up in front of McDonalds on the Prado at 8 am and the scores of others plying the streets of La Paz was its roof rack stacked with eight mountain bikes. McDonalds was the meeting point, and from here we'd drive the 26km (16 miles) uphill to La Cumbre, the start of the bike ride. On the way we passed through Villa Fatima, from where buses to Coroico depart, and then through the tranca, a police checkpoint found on the edge of all Bolivian towns. Aymara women, bundled in their shawls against the chill, sell drinks and snacks; and an unlikely looking priest in a blue boiler suit offers, for a small renumeration, to bless vehicles for a safe journey ahead.

The road to La Cumbre (the 4,725-m/15,500 foot) high point of the La Paz-Yungas route) is smooth asphalt passing through a dour landscape of steel-grey rocks, coated with a light dusting of snow, and hardy vegetation reminiscent of the highlands of Scotland. But for the llamas that graze by its side, the reservoir Laguna Inkachata could well be a loch. On a clear day, the icy summit of Huayna Potosi, the most popular mountain to climb in Bolivia, can be glimpsed.

Plenty of stray dogs loiter by the side of the road, waiting for the scraps of food Bolivians always chuck to them. Some people believe the dogs are the reincarnated souls of those who have perished on the road, but if that's the case there should be hundreds more. Many small tombstones and crosses line the way; in one incident alone in 1983, over 100 campesinos (people of the countryside) died when the lorry they were hitching a lift in plunged into the jungle. For bikers, these dogs are one more obstacle on the road; if they snap at you, Alistair's advice is to "bark at them madder and meaner than they do."

The Ride Begins

It had been chilly in La Paz, but at this altitude it's even colder. Leaving the minibus at the desolate La Cumbre plateau, crowned with its statue of Christ, I was glad of the extra layers of clothes I had been advised to bring. Between March and May you can expect snow here. Activity is also more of an effort in the thinner air, so it's a good idea to acclimatize in La Paz for several days before undertaking any mountain ventures, such as this bike ride, or trekking the Choro Trail to Coroico (see below), which starts at the same spot.

More Mountain Biking Options

There are two other main 1-day tours offered by Gravity Assisted Mountain Biking. The first takes you 36 kms (22.5 miles) from Chacaltaya to La Paz; the second is a 45-km (28-mile) route from the Zongo Pass to the Sud Yungas jungles. At 5,345m (17,535 feet), Chacaltaya is the site of the world's highest, developed ski-slope, serviced by South America's oldest (dating from 1940) and most dangerous ski-lift. It's been described as the world's only blue ski-run with a black ski-lift. Better to admire the spectacular mountain views of Illimani, Mururata and Huayna Potosi, and then do the bike ride down the scree slope and along an old mining road back tot he city. There are rough sections on this ride that the inexperienced cyclist might feel happier walking, and everyone will have to push the bike up the initial 45 vertical metres from the car park to the start of the ride.

The Zongo Pass ride starts at 4,780m (15,680 feet), on the pass at the access point to the peak of Huayna Potosi. Alongside the dirt road, which has a few flat stretches, there is a vertical, 3,500m (11,480-foot) drop into the steamy jungle. You'll pass llamas and alpacas in the higher reaches and waterfalls below…

Before the warm-up ride around the shallow pond at La Cumbre, Alistair gave us a short lecture on how best to ride the bike (see below), and on some of the obstacles (apart from the dogs) to be aware of on the way down.

Biking Tips

· Use the back brake as much as possible and handle the front brake with care. The front brake has 70 percent of the braking power and, if you're travelling at speed, a sudden squeeze is likely to send you over the handle bars.
· On the corners, use only the back brake, and go round with outside pedal down, your weight pressing onto it. Lean the bike in a little bit, but keep your body upright.
· Don't look directly at obstacles but at the point you're aiming for; by doing this you're more likely to skirt obstacles safely.
· If you sit down the whole way, your bottom will be so sore you won't be able to sit down afterwards. On the corners rest on the back of the seat; and on the straight, don't sit at all. Keep knees bent to absorb the shock, and let your thighs grip the seat.

We were to start on the right side of the road but would have to move to the left when the when the asphalt stopped and the gravel began. There's one tunnel, and we were to remove our sunglasses before entering it. When passing through the couple of small villages along the road, we were to slow down; colliding with a chicken or small child would be disastrous.

It was reassuring to know that if any of us had a puncture or worn brake pads -- either of which is not unlikely given the punishment the bikes endure during the descent -- a guide at the rear of the group carried spares and a repair kit. At two places along the route the brakes and tyre pressure would be checked, and there would be plenty of other breaks to allow us to have a snack (chocolate and fruit) and take photographs.

The ride began in awe-inspiring fashion. We whizzed down a wide, level road that meanders wildly through a v-shaped valley between jagged spurs of rust-brown mountains. A stream tumbles along the bottom of the valley, electricity pylons marching by its side, and clouds drift in among the spurs. On one slope, a zigzag path leads to a glacier, down which mules cart ice used to preserve the freshwater fish brought from the rivers beyond the Yungas to La Paz. The low, metal barriers on the curves are crumpled and misshapen from collisions; but I tried not to think about that.

Through the Cloud Forest
An hour later, we were pausing for a late breakfast of coffee and fried-egg sandwiches at one of the refreshment shacks that line the road beside the drugs checkpoint at Unduavi. The lush Yungas is a major producer of coca leaves that can be turned into cocaine, and it's a condition of American aid to Bolivia that this checkpoint inspects all vehicles on the road. Already we'd dropped 1,500m (4,920 feet), and the sharp wind has cut through to the bone. From here to the start of the gravel -- roughly 4 km (2.5 miles) -- is a series of small uphills with one 200-m (220-yard) long slope that gets the blood pumping again.

The clouds closed in, creating a wall of for that shrouds the landscape and provides the damp conditions for the prolific growth of ferns, mosses and other plants, across the rocky cliffs. At the crest of the hill, the road splits and we took the leg heading to Nor Yungas. Near by we passed the engineering works for the new road to Coroico, which is largely completed save for a major tunnel. This new route is designed to be safer than the one I was using, but it is not expected to be ready for a long while yet. In the meantime, the ugly evidence of its construction is apparent in the broad scars of red mud that blight the forested slopes lower down the road.

Just before we switched, as Alistiar put it, to the "scenic side" of the road (i.e. the side on which there are sheer 1,000-m/3,280-foot drops), we stopped for another safety briefing. From here on, downhill traffic passes on the outside of the road. The idea is to get vehicles to slow down, and it ensures that drivers with the best view of their outside tyres -- and the cliff edge -- do the risky backing up if faced with oncoming traffic on the narrow patches. Although it would often be possible for us to squeeze past vehicles, we were not to attempt to overtake until Alistair had given the OK signal.

Down to Coroico
The true nature of the road remains hidden in the clouds for several kilometres but, as we emerged into the sunshine, its full beauty -- and hideous danger -- became immediately apparent. I paused to marvel at the buses, lorries, and cars, slowly making their way along the ledge precariously cut into the hillside; and on one particular tight corner, I gawped in horror at the twisted remains of a truck scattered across the vegetation hundreds of metres below.

When faced with lorries, swaying along the road like unsteady elephants, their brimming loads of bananas and other produce always topped off with hitching campesinos, it's not a difficult decision to give them right of way. By this point in the journey, I was feeling more confident on the bike, but my hands ached from constant braking and I was glad of the opportunities to rest. Now that we'd hit the moist wall of heat riding up from the Yungas, we also paused to strip off layers of clothes.

Streams cascade down the rockface, creating muddy puddles on the road. In one place we actually rode under a large waterfall. By the time we'd reached the end of the ride at Yolosa, at 1,110m (3,600 feet), which is nothing more than a shabby pit stop at the river crossing in the valley, the road had dried and our wheels were throwing up clouds of dust. It was no wonder that Alistair jokingly promised that anyone who finished clean would get their money back.

Filthy, exhausted and exhilarated, we boarded the pick-up trucks that were waiting at Yolosa to transfer us up to Coroico, the small town perched on the shoulder of the hill Cerro Uchumachi. It's no surprise that this picturesque place, with its laid-back community, excellent views of the mountains and the fertile Yungas, and its good accommodation, food, and pleasant year-round temperatures, is a favorite retreat for travelers and locals alike. More importantly for me at the end of my ride, it also had, at the Hotel Esmeralda, perhaps the best hot-water showers in Bolivia.

Going It Alone

Internal Travel
About the safest way to travel down the appalling road to Coroico is by minibus, unless you are on a bicycle or in your own 4-wheel-drive vehicle. Minibuses leave regularly from the Villa Fatima area of La Paz; expect to pay around 15 Bs. Both Flota Yunguena and Turisbus Totai are reliable bus companies.

If you wish to make the return minibus journey from Coroico at a specific time, it's important to book ahead in the town because the buses quickly fill, especially on Sundays.

Bolivia is not an ideal place to hone your driving skills, but if you're thinking of hiring your own vehicle, go for a 4-wheel drive; check the tyres and brakes, and also hire a driver.

When to Go
The best time for visiting Bolivia is in the dry winter season between April and October, with the most favourable weather between June and August. Between La Paz and Coroico, you should be prepared for temperatures ranging from 4C (39F) to 30C (86F) and increased humidity in the jungle. The rainy season is between December and March, during which time Gravity Assisted Mountain Biking shuts down its operations… for your safety.

Planning Your Trip
For mountain bike tours, the best agency in La Paz is Gravity Assisted Mountain Biking …

CUT TO THE CHASE: Show me the photo slideshow of the World's Most Dangerous Road (in a new window)!!!

Many of the other tour agencies in La Paz offer organized treks along the various routes heading into the Yungas, including guides and equipment.

If you want to go solo, it's possible to hire equipment such as tents and sleeping bags in La Paz, if you haven't brought your own. Also consider putting a note up at the most popular travellers' hotels if you're looking for trekking companions.

You'll have no problem finding accommodation to suit your budget in La Paz, which is well served with hotels and restaurants.

In Coroico there is a similarly good range of tourist facilities available, but it's important to book ahead if you want to be sure of staying at a particular hotel, especially on a weekend or over major holiday periods.

What to Take
For the Bike Rides:

· A thermal jacket or sweater; these can be purchased cheaply in La Paz.
· Sunglasses.
· Bandanna.
· A replacement battery for your camera; the cold at high altitude often causes batteries to stop working.

Finally a hostel in La Paz everyone can and DOES recommend!! Lonely Planet: South America on a Shoestring (2007) says: "Adventure Brew Hostel. The name says it all. This brand-new abode on the block offers designer-style rooms, funky communal spaces, pancake breakfasts, as well as fun on tap. Yes there`s an authentic microbrewery on site.". Pg 192.