Colombia: The big chill

So specifically pinned to the atlas is the Caribbean that I'm feeling disorientated. And yet here I am, in Colombia, driving towards the promise of the sunrise, with that famous island-sprinkled sea on my left.

Not that any scattered archipelagos are in view here. Instead, I'm confronted by the stark outline of Colombia's north coast, the land plunging precipitously to the waves. Maybe it's the angle of the morning light, but today the Caribbean Sea resembles a plain of silver-turquoise concrete, the sun bouncing off it with intense ferocity.

I pull the car over into the shade of a cluster of palm trees and reassess the scene. No — this is not the powder-white-sand Caribbean of Barbados or Antigua. This is a flinty and unflinching South American version, all open water and hard corners.

It's also what I was hoping to encounter. Already, everything urban is nine miles behind, fading into the rear-view mirror as a welcoming party of boughs and branches begins to threaten the camber of National Route 90. But then, I'd not expected town life to put up a fight. Founded in 1525, Santa Marta may have been the first Spanish city in Colombia, but it can't claim to be a vast conurbation, puffing out its chest just enough to be the third largest dot on the country's Caribbean shore — after Barranquilla (60 miles west) and Cartagena (140 miles south west). That it stands as the capital of Magdalena says more about the second most northerly of Colombia's 32 departments — that it's unspoiled and scarcely over-populated — than it does its key port and guardian.

As if to emphasise this point, Route 90 makes a languid swing right, and the Caribbean Sea disappears, obscured by a thick blanket of green. The GPS informs me I'm 160 miles west of the Venezuelan border, skating along the roof of a continent — but I'll encounter my target before I have to deal with frontier officials and customs questions. Long before. Tayrona National Natural Park would be a fitting end to a road trip of many days. That it's now just four miles beyond my grasp is a near-palpable thrill.

There are further hints that I'm out on a limb. As I forge onwards, the 90 flashes across the Rio Don Diego, an impressive coil of coppery currents, but just one of the 36 rivers that unfurl from the curves of the Sierra Nevada de Santa Marta — which strafes the sky here, its peaks clawing the clouds. These mountains also help to make Tayrona an enclave of astonishing biodiversity — 70sq miles of land and sea where the altitude rises to 2,950ft on stoney summits, and crashes to a flat-lining zero where breakers roll in.

I glance at the range. Somewhere up there, eyes gaze back. The Sierra Nevada de Santa Marta is host to indigenous tribes who, while not entirely removed from the modern world, are not desperate to engage with it either. Both the Kogi and Arhuaco keep their own counsel on these foliage-drenched gradients, gathered into discreet villages and settlements, their agricultural way of life unaltered for centuries.

This is a trend — for Tayrona specialises in the elusive. This much is clear when I pass through the main entrance. Beyond the parking area, a wooden board salutes the presence within the park of the cotton-top tamarin — with a reminder that, though the monkey is endemic to Colombia, it's also endangered; translated into English, it reads, 'If it disappears in our country, it vanishes from the planet'.

I can't decide if this means Tayrona offers my best chance of seeing this rare beast, or that I'm being told my chances are slim. Maybe both. And yet, I'm unlikely to depart the park without meeting some of its inhabitants. Over 100 types of mammal skulk in its undergrowth or hang in its shadows, including the oncilla (a wildcat), plus around 70 bat species. Over 300 varieties of bird haunt its canopy, including the black solitary eagle, a dark predator that might be a vision from a nightmare in a less beautiful context.

An intense, persistent heat pulls at my legs as I set off down the three-mile trail to the beach. The path is rutted; gnarled roots snag my stride. Humidity wraps its clammy arms around me, the leafy walls on either side alive with avian chatter and insect burble. Only when I reach the shore does a breeze make itself felt. It's a relief to hear the rustling of palm fronds.

I emerge onto sand pockmarked by colossal granite boulders. Again, I remember this is the swarthy Latin incarnation of the Caribbean — although relaxation isn't an alien concept. A crowd is gathered at the tide's edge — weekend Magdalena casting off its cares.

There are no five-star hotels here, no towering condominiums. Just a glorious simplicity of existence — and another board, declaring that this seafront has long been regarded as sacred by the Kogi and Arhuaco, who come to the beach 'to pay tribute to Mother Earth'.

Certainly, a respectful calm is detectable. On Playa La Piscina, a vendor sells cans of lemonade from a cool box for 4,000 pesos (£1). Pricey for this part of the globe, but the temperature is soaring, and he has customers. On neighbouring Playa Arenilla, a basic cevicheria serves portions of marinated shrimp and fish; a stack of limes balanced on a shelf behind. Everyone is eating. In front of the stall, a gecko darts out a tongue to trap a cockroach bigger than its head, then lies discomfited, stomach bulging, all its Christmas dinners come at once. In the shallows, a young mum teaches her little boy to swim, cradling his body on the surface as his legs flicker in panic.

Perhaps he's right to be nervous. As I wander back along the shore, I notice a tiny lagoon, separated from the sea by a narrow sandbar. A third sign advises that an alligator lives here. And there it is, its eyes blinking above the water. I smile, imagining the furore if this snap-jawed reptile were to make itself comfortable on any European tourist beach, and contrasting this with the laissez-faire attitude on display here. But then, in a country where guerilla devilry and civil war were, until recently, an everyday reality, a potentially dangerous lizard might not be considered extraordinary. Tayrona National Park, on the other hand, is exactly that.

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Published in the South America supplement in the October 2015 issue of National Geographic Traveller (UK)