Our destination is a remote finca, or farmstead, inside the wild, mountainous rainforest that spans the isolated isthmus between Colombia and Panama.

For decades, the isthmus, a narrow strip of land known as the Darien Gap, had been notorious for killings, kidnappings and drug trafficking.

But with the recent onset of a fragile peace in Colombia, the Marxist guerillas of the Revolutionary Armed Forces of Colombia (Farc) have moved away, leaving what we have expected to be a pristine jungle waiting to be explored.

It does not turn out like that. As we trudge along the muddy trails, we find plenty of signs that others have preceded us - discarded clothes, broken shoes, empty water bottles. Then, at the very end of our two-day trek, we round a corner and find 17 terrified migrants staring at us.

They are men and women, Haitians, Congolese and Togolese, all bound for the United States, but pathetically unprepared for this most perilous stage of their marathon journey.

They have no guide and the Darien Gap is so impenetrable that it forms the only break in the 30,000km Pan-American Highway between Alaska and Argentina.

They have no protection against the debilitating heat, violent tropical storms, malarial mosquitoes, poisonous snakes and wild animals. They wear cheap plastic sandals and carry packets of biscuits in flimsy carrier bags.

We warn them that other migrants have perished trying to cross into Panama, that they will never find their way alone. We urge them to hire a guide in Capurgana, the remote fishing village on the Caribbean coast to which we are heading. But in vain. They have little or no money.

What has become of those wretched migrants, I have no idea. I admire their determination to risk so much for better lives and wish I can help them more.

I am also acutely conscious that I have undertaken for mere adventure a trek which is, for them, a matter of life or death.

GOLDEN BOGOTA

If Colombia's peace holds, this vast country looks set to become one of the world's hotter tourist destinations, as Farc relinquishes its grip on great swathes of Amazonian rainforests, remote Andean valleys, Pacific and Caribbean coastlines.

Moreover, a silver lining to Latin America's longest and deadliest insurgency is that it has prevented the commercial exploitation and destruction of the wilderness, keeping it relatively pristine. The 7,500 sq km Darien Gap will, I hope, be a case in point.

A colleague and I duly fly to Bogota and are enchanted by the lively, colourful capital. We stay at the Hotel de la Opera (www.hotelopera.com.co), a charming colonial-era edifice in the historic old Candelaria district, and spend a delightful day exploring the city's many wonderful free museums.

The Musee del Oro (www.banrepcultural.org/gold-museum) contains thousands of the ornaments, religious offerings and other stunning gold artefacts from the pre-Hispanic era, which inspired the legend of El Dorado.

The Musee Botero (Calle 11 No 4-41) contains not only the magnificent private art collection of Colombian artist Fernando Botero - Renoirs, Monets, Picassos and Dalis - but also scores of Botero's own trademark depictions of grotesquely voluminous figures.

At the Police Museum (Calle 9 No 9-27), we inspect the customised Harley-Davidson of late Colombian drug lord Pablo Escobar and a bloodstained tile from the roof on which he was shot.

We eat a sumptuous lunch of New Colombian cuisine at Restaurant Leo and roasted ants purchased from a street vendor. We admire another of Colombia's artistic specialities - the huge, fantastical murals that seem to cover every wall.

Towards evening, we take a funicular up a hill called Cerro de Monserrate and enjoy spectacular views across Bogota to the distant peaks of the eastern Andes.

CITY OF ETERNAL SPRING

The next day, we fly on to Medellin, which was the world's cocaine and murder capital when Escobar's cartel controlled it in the 1970s and 1980s. Today, the City of Eternal Spring - a reference to perfect climate - is as safe as New York or London.

Fancy new highrises dot the floor of the steep Andean valley in which it sits. An impressive new metro dissects that valley. Cable cars serve the shanty towns that cling to its sides. There are fine parks, squares and libraries, and the young hang out in the hip bars and restaurants of Parque Lleras.

Earlier this year, Medellin won the Lee Kuan Yew World City prize for innovation and sustainable urban development.

Eager to look forward, not back, the city's authorities discourage the unofficial Pablo Escobar tours on offer, but we take one anyway.

Mr Carlos Palau, a former policeman whom the cartel targeted several times, shows us the luxury apartment block - now derelict - where Escobar lived with his family in the penthouse and tortured prisoners in the basement; La Catedral, the luxurious hilltop "prison" - replete with helipad and "pleasure rooms" - that Escobar built when he agreed to voluntary incarceration to avoid extradition to the United States; and the suburban safe house where he was shot dead in 1993 as he sought to escape across a roof.

People still lay flowers at Escobar's grave in the Montesacro cemetery because he assiduously curried favour with the poor by building them homes and football pitches.

Mr Palau prefers to pray at the grave. "Look at you, Escobar," he intones. "You tried to kill me many times, but you didn't. I win. Thank you, because now you're in the ground and I'm making money in your name."

CAPURGANA'S EDGY CHARM

The next day, we leave the proverbial beaten track and fly north to Acandi, a town on the Gulf of Uraba far from any road.

From the tiny airport, a horse and cart convey us along a shady track to an open boat which speeds us out of the Gulf and along the rocky coast to Capurgana some 40 minutes away. There, a man carries our luggage from the jetty to our hotel in a wheelbarrow for there are no cars.

Capurgana has an edgy sort of charm. Some brightly painted bars and hostels serve the adventurous tourists who reach the village. The Afro-Colombian locals play cards or dominoes in the heat, the hammock is ubiquitous and torpor prevails.

But a large hotel owned by an extradited drug trafficker stands empty beside the beach. Young paramilitaries keep a discreet but watchful eye on new arrivals and one suspects they engage in the odd bit of drug or human trafficking into nearby Panama.

We hike to Panama the day after our arrival, cooling ourselves in a waterfall on the way and lunching off fresh red snapper at a tiny beach resort called La Miel, before hitching a ride in a small boat back to Capurgana.

We swim. We sit in a natural pool while tiny fish nibble our feet. At night, we eat delicious seafood at a beach hut called Josefina's, whose plastic chairs and tables are lit by a single light bulb hanging from a tree. Far offshore, an electrical storm provides a spectacular son-et-lumiere.

JUNGLE ADVENTURE

On the third day, we set off early in the morning for what was supposed to be a relatively easy three- or four-hour hike to the finca in the jungle. It proves anything but.

This is no Disney jungle. There are no groomed and graded paths for tourists. For hours, we squelch along tracks ankle-deep in thick red mud, labouring up endless steep ridges and fording rivers in the valleys.

In no time, we and our clothes are soaked in sweat. We are hemmed in by dense tangles of vines, creepers and roots, palms and giant bamboo. Above us, 30m-high trees obscure the sun and sky.

There are compensations, though. We see exotic birds galore - primary-coloured toucans, crimson-crested woodpeckers, king vultures, white hawks, iridescent humming birds, manakins, parakeets, flycatchers and caracaras (Colombia boasts a world-record 1,900 species of birds).

Primary-coloured butterflies with 15cm wingspans flutter past, jerked by invisible strings. Capuchin monkeys swing through the foliage overhead. Howler monkeys cry in the distance. Flaming red flowers light up the forest and at streams with deep clear pools, we flop gratefully into the cool water.

But the jungle is scarcely pristine. The trail is littered with discarded rubbish and belongings of migrants heading north. Once, we encounter two young "coyotes" - migrant smugglers - returning from the border, one armed with a revolver.

After eight gruelling hours, we finally reach the finca - a clutch of well-kept cabins spread out like a mirage in a clearing below us. Eider and Andres, the two young men who run the place, give us sweet lemongrass tea to revive us. We bathe our exhausted bodies in an adjacent river.

Over supper that evening, we learn that the finca - La Paloma - is owned by Mr Jorge Henao and his wife Maria Elena, bar owners in Capurgana who fear some sort of apocalypse and want a bolt hole.

They bought it nine years ago when Farc still controlled the jungle, but the guerillas let them stay so they could steal their produce.

Today, they keep chickens, turkeys, pigs and ducks. They grow rice, yucca, plantains, beans, pineapple and guava. Eider says that hundreds of migrants pass through the jungle each month and that some die of snake bites, heart attacks or childbirth, but they avoid the finca.

That night, we hunt for giant croaking frogs with flashlights. We catch langoustine in our torch beams in the river, then slice their heads off with machetes. Later, a ferocious tropical deluge hammers on the cabin roofs as we fall deep asleep on camp beds.

I hanker to stay. Eider and Andres see panthers and jaguars around the finca and 3m-long boa constrictors near the river. There are fine pools for swimming. We could have ventured deeper into the jungle. But we have planes to catch and schedules to keep, so we return to Capurgana the following day - meeting the 17 migrants en route.

That evening, we find Mr Henao and his wife in their bar, the Luz de Oriente. They say they want tourists to visit the finca. They need their support as they fear the Darien Gap will be destroyed by loggers and miners, now that Farc has gone.

"Peace is a mixed blessing," Mr Henao says. "The conflict was what kept it pure and unspoiled."

•Martin Fletcher, a former foreign and associate editor of The Times of London, travelled as a guest of Steppes Travel.