It's not a great start. At the beginning of one of the most beautiful walks in the world I am confronted by a big yellow sign. It warns, in three languages, that if I go any further I might get hit by a landslide and that, anyway, my destination – the sea, for heaven's sake – is closed.
Never mind. There are, in fact, two good reasons for continuing down into the fabulous Masca Gorge in north-west Tenerife. One is the fact that dozens of other people are fearlessly doing so even as I stand hesitating on the edge of the path. The other is even better: as my guide Pepe explains with shrugging dismissal, the local authorities put the notice up just to cover their backs.
Apparently there have been landslides in the gorge and the beach at the end was closed for a while after one particularly big fall. But in general, Pepe insists, it's all fine. "We go!" he says. So we do.
Never mind the bars and all-day breakfasts of Tenerife's famously sedentary southern beach resorts, it really is possible to find sharper pleasures on this strangely polarised island, especially if you head north and go about it the right way. Even our drive to the small, isolated village of Masca itself was surprising – a matter of twisting mountainous roads and staggering views over lush wilderness.
Then came our arrival, which at first was more like the Tenerife I'd expected, with crowds overwhelming the village shops and cafés. Every visitor was seemingly intent on doing the Masca Gorge walk: eight kilometres from mountain to seashore, three or four hours each way, astonishing views predicted by those in the know. I was desperate to find a hidden Tenerife, somewhere better than beaches and sangria – but would that be possible here, among this mass of humanity?
As I walk towards the 600-metre depths of the valley bottom, I quickly discover that isolation is not, after all, an essential ingredient if you're looking for paradise on foot, though it's hard to explain why. The place is... remarkable. Atmospheric. No, that hardly does it justice. Masca Gorge is so visually rich, so stunningly varied in its rock formations, in its flora, in its sense of place and even its climate that you feel bewildered by the experience, almost overwhelmed.
It is scrambly at times – and slippery, too. Once, I swear I even hear rocks falling. But in general there is a kind of stifling peace, the narrow, twisting path demanding little that a moderately fit person can't provide, the vast walls keeping much of the sun at bay so no-one bakes. It's the cliffs, though, that are the most impressive part. Whether I'm clambering over smooth volcanic boulders, jumping over tiny ponds or swerving round intensely lush clumps of wildflowers and white broom, the canyon sides create a central drama that is impossible to ignore. They soar in a mass of twisted volcanic complexity, holed and striated, shaded into a thousand tints of orange and grey and ochre and brown so that when we pause for water all I can do is lie back with my head on a rock and scan the shapes endlessly, up and up to the very rim on the canyon where the cliff edges are serrated like torn paper.
The people eventually get in the way a bit. At one point I have to queue to get past a particularly awkward set of boulders as slower walkers take it oh-so-carefully. But it doesn't matter. Arriving finally at the tiny beach, the sense is of a journey ripped from the jaws of Tenerife's more traditional style of mass tourism. The business of getting back to civilisation needs to be sorted out in advance, by the way: through your hotel, or in the village of Masca, book a boat ride – for around €15 (£13) – to the nearby resort of Los Gigantes.
Next day is brilliantly sunny again, but windy now. Yesterday's sense of rescue continues. Still in the mountainous north-west, I rent a kayak at La Punta de Teno and join a small group heading seaward. Vast, pitted sea cliffs shoot up from choppy Atlantic waves as we make haphazard progress, the sun burning holes in my T-shirt. After half an hour of paddling we arrive at a sea cave that swallows us up.
It's vast inside. Our boats rise on swooping waves so that we feel disorientated in the semi-darkness, barely bothering with paddles, mostly just listening to the wind on the cave mouth. Then we roll off our boats one by one to swim around and around in the half-dark, excited as children. When we've had enough we somehow struggle back on to our kayaks, almost tipping as we haul ourselves up, fumbling for the paddles again, pushing back out into the shocking sunlight.
The wind is higher now, hard in our faces as we turn towards the beach, shoving us off course the moment we ease up for a second, cliffs and rolling landscape to the right, the Atlantic Ocean to the left broken by an outcrop of islands and white-tops and nothing else. At this point I re-encounter that sense I had in the gorge, that this overdone island might be tame on the surface, but is wilder – better – at heart.
I meet three or four guides during my stay. All are anxious to talk about exactly this sense of "different" tourism. They eagerly point out that nearly half the island is now protected by law. It's a change driven by the fact that cheap beach holidays are now available pretty much everywhere, but this landscape is special.
In Teide National Park, in the centre of Tenerife, the eponymous volcano rears to a white-topped 3,718 metres, complete with a cable car and crowds. Yet you can avoid the crush simply by picking one of 34 waymarked lower routes that thread this cindered, crunchy moonscape. I try a couple of these walks for myself and find them starkly beautiful, like trekking through fragile filmsets (parts of Star Wars and Clash of the Titans were shot among these cathedral boulders).
It isn't all sweat and staggering views, of course. Each night I potter tamely back to one of the growing number of modestly sized but pleasant hotels that are gradually popping up in Tenerife. At the Vincci Selecció* Buenavista Hotel I sit on my balcony in the bright evening light staring at a golf course. Then, in the morning, I look for adventures again.
At the end of my trip I clamber though a bleak subterranean lava-tube called the Cueva del Viento, while a man with a lamp on his head tells me about magma and pyroclastic streams. Above us water drips and plant roots struggle blindly into open space as the earth gives way to hollowness.
It's all very interesting, very moody; but what I really remember is the green and rocky surface and the genuine surprises waiting up there beyond the bars and sunloungers.
The writer travelled with Monarch (08719 40 50 40; www.monarch.co.uk), which flies to Tenerife South from Birmingham, Gatwick, Luton and Manchester. The same airport is also served from a wide range of UK airports by Ryanair (0871 246 0000; www.ryanair.com), Jet2 (0870 910 1000; www.jetair ways.com), easyJet (0843 104 5000; www.easyJet.com), Thomson (0871 231 4787; www.flights.thomson.co.uk) and Fly Thomas Cook (0871 230 2406; www.flythomascook.com).
For boats to Los Gigantes from Masca Gorge beach, see www.mascalosgigantes.com
Vincci Seleccion Buenavista Golf & Spa Hotel (00 34 922 06 17 00; www.vinccihoteles.com). Doubles start at €114, including breakfast.
Tenerife Tourist Office: 00800 100 101 00; www.webtenerifeuk.co.uk