Every good journey in Bolivia starts with a shot of moonshine and an offering to Pachamama, the Mother Earth. This one is no different. On a bright but autumnal Bolivian morning I'm standing at La Cumbre, the entrance to Cotapata National Park some 28km from downtown La Paz, knocking back a throat-scorching gulp of singani, the local brandy. My guide, meanwhile, is busy preparing the ch'alla, or offering, to ask for Pachamama's blessing on the trail ahead. I look on as he sprinkles coca leaves and splashes of hooch on the rough earth at the foot of the statue of Christ the Redeemer, then I strap on my boots and rinse my mouth from my water bottle. Coroico is 52km of wilderness, or three days on foot, to the east – and there's no turning back.
The Choro Trail is the best-known of Bolivia's spectacular, high-altitude trails. It offers more scenic contrasts than most, with a trailhead amid the snow-strewn 4,000m-plus peaks of Bolivia's Cordillera Real and a descent through lush sub-tropical valleys to the Yungas region, which lies at less than half the altitude. Better still, it feels gloriously unexplored, with empty trails shrouded in mountain mist and near-deserted campsites along its length. With fewer than 2,000 trekkers per year (compared to the 500 people still jostling elbows along Peru's Inca Trail each day), there's a sense of remote tranquillity.
The first morning of the trek feels like a classic Altiplano hike, with the windswept path forged across rough-hewn rocks and bare, open pasture. As I get into my stride, I pass the occasional adobe shack, or a weather-beaten farmer tending his flock of llamas. There's a stop for lunch at the remote pueblo of Samaña Pampa. Andean condors soar overnight as I devour my sandwiches and flask of coffee. A perfect sense of calm reflects off the mountain as far as the horizon.
The afternoon, however, brings the first real test of my trekking mettle: blisters. The trail may be well marked, but the route makes for steep, downhill progress at times. My knees and feet take the full brunt of the descent. By the time we stop to rest at Chucura, a huddle of lost-in-time village huts at 3,600m, I'm imploring Pachamama to save me from the hell that is the grinding friction of ill-fitting hiking boots on a precipitous decline.
I make it to the camp at the small village of Challapampa at dusk, tired, hobbling and woozy from the dull ache of my throbbing feet. As I collapse into my sleeping bag after a supper of soup, macaroni and sugar-coated bananas by candlelight, I fear our offering had failed to please the capricious ancient spirits.
The next morning I awake to find the gentle glow of sunshine warming the tent and the cooling water of a nearby brook to freshen up before breakfast pancakes. In the daylight, too, I can see how the landscape is starting to change: from the high-altitude Altiplano of the previous day to the lush semi-jungle of the Yungas. Our tents are pitched in a green clearing fringed by wild flowers and the path ahead looks softer, grassier and, mercifully, more even.
It's a hot and sweaty descent following the River Chucura, but orchids and butterflies bring exotic splashes of colour to the trail. The lunch stop is at Choro, where four families live in a cluster of broken-down shacks by the river. An old crone flashes a smile that attests to a lifetime of poor dental hygiene as I buy one of the greasy bottles of water she hawks to the occasional passing trekker.
The next stage is a slog uphill to the tiny pueblo of San Francisco. The friendly locals have converted farm stores into rudimentary shelters and rigged up a makeshift shower with a drip of water and a platform overhanging the lush, palm-fringed valley. The view as I'm sluicing my aching muscles before bed is quite spectacular.
The last day starts with a heart-in-mouth scramble over slippery rocks under a cascade of water. After crossing the River Coskepa, we start the steep incline of the Devil's Hill, a 45-minute yomp over ancient steps with views across the banana and citric fruit plantations. The leafy Yungas village of Sandillani is home to Tamiji Hanamura, a Japanese hermit who runs a small campsite in his orderly back garden, complete with picnic tables. As we open our snacks and rest our aching feet, Tamiji-san peers out from behind the garden fence like a forest spirit: tiny, wizened and stooped over with the weight of his grubby baseball cap. He came to Bolivia as a traveller and fell in love with the Yungas scenery; painfully shy, he has, he tells us with some pride, not even ventured as far as the next village in more than 10 years.
The final leg of the trek descends towards Chairo, a village on the shores of the River Huarinilla, where buses and trucks connect to Coroico, the transport hub of the Yungas. It's a soft decline for the first hour but then, just when you think it's all over, there's one final crushing irony: a steep descent over loose stone fragments in a zigzag formation. Halfway down, scrawled across a huge trailside rock, some graffiti reads: "I'd prefer to die of the pain in my feet than to continue walking on my knees."
Finally, I stumble into Chairo on a sunny Yungas lunchtime. It's a biblical moment for many trekkers. Some cast themselves into the water to be reborn, others fall to their knees sobbing and clutching their blisters. I found the only working fridge in Chairo and handed over a few bolivianos for my first genuinely cold soft drink in three days. But before I took that first delicious, thirst-quenching sip, I sprinkled some of the liquid on the earth at my feet. I owed Pachamama a debt of thanks.
David Atkinson is the author of 'Bolivia: The Bradt Travel Guide' (£14.99)
Getting there and around
The best connections from the UK to Bolivia's capital, La Paz, and the city of Santa Cruz, are on American Airlines (020-7365 0777; www.americanairlines.co.uk) via Miami. If you prefer to avoid the US, Aerolineas Argentinas (0800 096 9747; www.aerolineas.com.ar) flies from Gatwick via Madrid and Buenos Aires.
To reduce the impact on the environment, you can buy an "offset" through Abta's Reduce my Footprint initiative (020-7637 2444; www.reducemyfootprint.travel).
The best agency in Bolivia to arrange trekking trips locally is America Tours (00 591 2 237 4204; www.america-ecotours.com), run by English-speaking Bolivians, which deals in low-impact walking holidays with an emphasis on community projects and respecting the environment.
The Hotel Rosario in La Paz (00 591 2 245 1658; www.hotelrosario.com) has been adapted from a 19th-century hacienda built, in typical colonial style, around a sunny courtyard dotted with plants. Doubles from US$50 (£27), including breakfast and internet access.
The Hotel Esmeralda in Coroico (00 591 2 213 6017; www.hotelesmeralda.com)has great views. Doubles from US$24 (£13), including breakfast.
British nationals receive a free 90-day visa upon arrival at La Paz or Santa Cruz. Keep a photocopy of your passport in your daypack at all times for identification purposes.
In theory, proof of vaccination against yellow fever is required (bring the certificate). The main problem in the Altiplano, however, is altitude sickness – take it easy at first and drink the local coca tea to help you acclimatise.
For more details about travel in Bolivia, contact the UK-based Latin American Travel Association (020-8715 2913; www.lata.org).