When you make it through the thicket of selfie sticks on the Ipapantis Walkway in Fira and see the caldera for the first time, a strange sensation may take hold of you. I've heard it referred to as Stendhal syndrome: a sort of derangement of the senses which means that whenever you're faced with scenes of beauty or the sublime, you turn into a complete vegetable. I don't know if the Santorini caldera counts but there's certainly something seriously intoxicating about looking over that unfathomable hole and the twinkling sea that surrounds it. And that's before a drop of assyrtiko has passed your lips.

Santorini's past reputation for producing powerful, high-alcohol, often oxidative wines or vin santo, the island's unctuous, raisiny sweet wines, has given way in recent years to a quiet winemaking revolution that the world is now waking up to. It centres on the island's main indigenous grape variety, assyrtiko. Santorini assyrtikos, lipsmackingly delicious as they are to drink now, have the ageing potential of the great rieslings of Germany, or the great chardonnays of Burgundy. Born of the harsh, unforgiving conditions that prevail the island, these are wines structured behind an adamantine-hard core, which means their evolution is very slow – they may take five, even ten years, before their flavours begin to properly unfurl – but their mouthwatering, flinty, volcanic character when they're young would make it a struggle for most to wait that long.

John Szabo, a Canadian master sommelier who recently published a (now André Simon-prize-winning) book on the subject, Volcanic Wines: Salt, Grit and Power, describes the agricultural produce of Santorini – the tomatoes, the fava, and of course the grapes – as having a "ferocious intensity" as a result of the extreme conditions. "Hardened like a Spartan warrior," he says, '"each is suffused with forceful flavour, an archetype of its species."

An unami character is common in volcanic wines

Santorini has been described as probably the hardest place on the earth to grow vines: searing summer heat and ferocious winds, with humidity either close to saturation point or almost zero, switching suddenly as the sun rises and winds pick up.

The vines here tend to be phenomenally old. Although the parts of the vines above ground on the island's sand, pumice and volcanic ash soils are around 70-80 years old on average (already very old in vine terms), the roots can be five or six times older. These old vines and ancient root systems are crucial to the concentration and minerality which so define Santorini assyrtiko.

The island's vinegrowers often use a propagation technique called head grafting. What this means is that at a certain age, old vines are decapitated and new ones are grafted on to the old root systems. Because Santorini is one of very few places in Europe that was unaffected by phylloxera – the vine plague which wiped out about two-thirds of European vineyards in the late 19th century, and which meant almost all new vines had to be planted on to phylloxera-resistant rootstocks – all of the island's vines remain on their original roots. Yiannis Paraskevopoulos of Gaia Wines estimates that the roots of his Santorini vines are 400-500 years old, which would almost certainly make them the oldest vines in the entire world.

Identifying a 'volcanic wine' in the glass

So-called 'volcanic wines' are becoming quite trendy in London at the moment, with adventurous sommeliers increasingly looking to add nerello mascaleses from Etna, zibbibos from Pantelleria, listan negro from Tenerife, even koshu from Japan or arinto from the Azores. Yotam Ottolenghi's restaurant Nopi even has a section dedicated to volcanic wines. But what exactly are volcanic wines? And what do they taste like?

Szabo talks about that minerality mentioned above, even a slight saltiness. In the case of Santorini assytrtiko, this saltiness is in part attributable to the sea spray (known locally as pousi), which leaves salt traces on the vines, but a certain umami character is common to a lot of volcanic wines. They are less about fruitiness, more about tense, mineral power. In the case of assyrtiko, a grape with an extremely low pH level and high acidity, this creates a wine whose peachy, honeyed rich notes are entombed behind this steely, salty, mouthwatering minerality. Over the years, the richness breaks free. Eventually petrol notes can emerge – similar to some fine rieslings.

If you love wine, and in particular mouthwatering, flinty, minerally whites – chablis, Mosel riesling, Tokaj furmint, all that good stuff – assyrtiko is a discovery you'll be glad you made, and doing so in the place it's made would make the experience all the more special. There are 22 wineries on the island, and if you do decide to go, there's three I'd strongly recommend you visit…

Gaia Wines

Gaia Wines is owned by bordeaux-loving oenologist Yiannis Paraskevopoulos. He also has an interest in the biggest brewery on Santorini – which is named, appropriately enough, the Santorini Brewing Company. Gaia's stated aim is to use state-of-the-art technology to enhance the potential of Santorini's native grape varieties – in effect assyrtiko, which accounts for 70% of the vines planted on the island.

The small winery is in an old tomato canning factory (Santorini produces the most intensely flavoured cherry tomatoes, and the best tomato paste, you'll ever taste), right on the beach in Kamari. Visit between April and October and enjoy a winery tour and tasting, then sit on the whitewashed porch over the shallow volcanic beach and listen to the waves lapping the shore with a coral-pink sun setting behind you and the island of Anafi, mythical refuge of the Argonauts, visible on the horizon. The airport is only about 15 minutes' walk away, so you hear planes taking off every hour or so in high season, but who are we to demand perfection?
You can find Gaia's wild ferment assyrtiko over here in the UK, and it's worth seeking out. The grapes come from upland vineyards in Pyrgos. The bigger day/night temperature range up here means longer ripening periods which, combined with some skin contact at cool temperature, helps to extract phenolics, giving you a peachy, minerally, umami-rich and powerful wine.

The sea spray which hits the low-lying vines on the island confers a salty character

Then there is Gaia's thalassitis. In bygone times, a mix of wine and sea water (sea is thalassa in Greek) was thought to have therapeutic properties. Yiannis doesn't add sea water, but points out that sea spray which hits the low-lying vines on the island does indeed confer a salty character. Gaia's oak-fermented thalassitis (he also makes one in stainless steel) is as deliciously creamy, toasty, tense and minerally as a really good meursault, and for a fraction of the price.

Hatzidakis

Robert de Niro is a big fan of Haridimos Hatzidakis's assyrtiko, apparently. When I visited the winery in September last year I was told that just a couple of weeks earlier he'd shown up at nearby restaurant Forty One pointing the owner to a picture of Hatzidakis's single-vineyard louro on his phone. "I want this one," the actor said, and duly got it. It's a wine made from 130-year-old vines and aged for two years in oak, and is, to be fair, an absolute stunner.

Winery owner Haridimos Hatzidakis used to work for Greek wine giant Boutari in Naoussa. For the past several years, however, he's been making wine for himself and gaining a serious reputation among wine enthusiasts. Recently he built a new gravity-fed winery, carved into the volcanic rock of the hillside in Pyrgos. His organically farmed vineyards benefit from higher altitude, which, as mentioned earlier, allows for longer ripening and better overall grape expression.

You can find Mr Hatzidakis's basic assyrtiko in Waitrose (a bargain at £15), but his more terroir-focused wines, such as the louro and mylos, are the serious gear. He's also a bit of a pioneer with a high-quality red variety called mavrotragano (which translates as 'dark and crispy'). He was the first on the island to plant this grape; now most of the wineries make one. If you ever find it, his 100% aidani is also well worth trying. Usually used in the island's traditional sweet wine, vin santo, or one that needs to be blended with assyrtiko to give it some backbone, aidani in Hatzidakis's hands is aromatic, zesty, flinty, buttery – absolutely delicious.

Sophisticated octopus dish served in a seashell

Domaine Sigalas

Domaine Sigalas is situated on the ancient plain of Oia to the north of the island. The tip of Oia is where many people converge to watch Santorini's legendary sunsets, though Sigalas is well away from the tourist hordes. The winery is owned by former mathematician Paris Sigalas and makes wine from assyrtiko, two other indigenous white grapes, aidani and athiri, along with reds mandilaria and mavrotragano.

I think, all things considered, this is my favourite winery on the island – that's partly down to the quality of the wines, partly because its lovely bar and terrace are perfect for whiling away an afternoon or evening (great food, freshly caught fish, wine tasting options and such like), and partly because of the infectious enthusiasm of Panayiota Kalogeropoulou, the winery's hospitality manager. A theatre graduate and former sommelier, Panayiota has so much energy and love for what she does, and is absolutely in her element talking to you about the wines, about gastronomy, and about which wine pairs best with which food.

Domaine Sigalas's single-vineyard Kavalieros was really my epiphany wine as far as assyrtiko goes. It's absolutely wonderful – fresh, citrusy, peachy and floral, yet deeply textured, mouthwateringly mineral and with an understated power (what John Szabo MS, paradoxically but sensibly, calls a 'weightless gravity'), which tells you that this is a wine that will evolve gracefully for many years to come.

Sigalas also makes a stunning nykteri – another Santorini speciality, made from late-harvest assyrtiko grapes – 20 days after the natural ripening. All the grapes used have been dehydrated on the vine by the botrytis – aka 'noble rot' – fungus.

ESSENTIALS

WHERE TO STAY

Aressana, Fira
A seriously luxurious hilltop hotel with a very impressive restaurant. Local chef Dmitri Papadmitriou calls his food 'nouvelle but not molecular', though you definitely get the sense that he's been poring over an El Bulli cookbook. Enjoy the tasting menu on the balcony overlooking the Aegean.

WHERE TO VISIT

Yiannis Nomikos Estate
It's estimated that soils of volcanic origin cover around 124 million hectares – about 1% – of the planet's surface, but provides sustenance for 10% of the world's population. So it is that on islands like Santorini, certain fruits and vegetables are among the tastiest versions you'll find anywhere in the world – it's why Santorini cherry tomatoes and fava have their own PDO. Yiannis Nomikos's visitor-friendly estate is an ongoing effort to standardise the wonderful agricultural products of the island.

WHERE TO EAT

Assyrtico WIne Restaurant, Fira
For a fantastic lunch within view of that hypnotic caldera, this restaurant takes some beating. With dishes such as fava with salted, smoked Cretan pork (apaki) mousse, you could easily end up gorging here all day.

Selene, Pyrgos
With its smart, creative dining showcasing local produce, dinner on the balcony at Selene is highly recommended. The sommelier-manager, Georgia Tsara, has been promoting Santorini wine and Cycladic cuisine for the past 20 years.

Nikta means night in Greek, which is traditionally when pickers would harvest the grapes for this wine. It tends to be a touch sweeter (though still on the dry side) and much more voluptuous than a simple dry assyrtiko. Panayiota recommends the Sigalas nykteri as a pairing with food as diverse as a stilton-type blue cheese or lamb/veal roasted with lemon.

Unacknowledged wonder of the world

Sigalas, Hatzidakis, Gaia – these wineries show what can be achieved on this extraordinary island when modern winemaking methods and sensitivity to the sense of place are combined with a volcanic terroir, ancient viticultural techniques and a very special native grape variety.

Because it's only been like this for 20 years, we don't know yet just how much ageing potential these wines actually have (the traditional ones wouldn't have been made so carefully, oxidation would have limited their shelf life). Given their pH and acidity, it's very likely that these wines will age like the great rieslings of the Mosel – some of the most revered wines on earth.

So much so that, having visited the island, tasted its wines and eaten its food, I'm going to put all restraint to one side to say this: you should book a flight to Santorini this very minute to enjoy the extraordinary wine, the food and the island itself. Because in spite of the selfie sticks, in spite of the fake wedding photoshoots and the models Instagramming their arses from infinity pools, the island is an unacknowledged wonder of the world. And to be there and sit back with a glass of chilled assyrtiko while a coral-pink sun sets over the Aegean is a blissful thing that you will be the poorer for never having done.

Want to learn more about wine? Why not check our our expert guide to choosing wine in a restaurant. Want to know where to taste assyrtiko wine in London? You'll find them at places like The Greek Larder and Milos – restaurants like these are doing a great PR job for Greek gastronomy, as is Theo Kyriakou of the Greek Larder, who puts on the excellent Greek Wine and Food Festival each year.