The first surprise is how suddenly Marseille surrenders the initiative. One moment the 21 bus is stuttering on Boulevard Michelet, mired in a traffic jam worthy of France's second-biggest city. The next its windows are alive with jagged ridges and the call of the wild. Mazargues seems to be the dividing point, the gilded homes of this affluent suburb falling away as if observing an unspoken border treaty. Beyond the invisible line, a harder realm waits. Rocky flanks rear up; dark, wide-winged birds wheel menacingly above, and there is a stark dryness to the scenery that feels rather more Wild West than southern France.
The second surprise is that I am surprised. Because when, just 45 minutes after I boarded it in the heart of the metropolis, the bus rolls to its last stop at Luminy, I find myself on the edge of one of Europe's most remarkable – and notoriously arid – geographical enclaves.
Les Calanques is Marseille's surly, brooding next-door neighbour – a striking pocket of untamed terrain that, though it lies barely 8km south-east of the grand avenue of La Canebière and the fluttering sails of the Vieux Port, is different from a city that will be a European Capital of Culture in 2013.
Here, millennia of fluvial erosion – the might of the Mediterranean hammering at the soft limestone of the shoreline – have carved a rugged wonderland where 24 narrow, sheer-sided channels (the word calanque translates loosely as "inlet") offer a gap-toothed smile.
Within, the land plays the percentages, ranging from sea-level serenity to the 565m summit of Mont Puget, the highest spot in the area. And wildlife skitters and darts across these craggy surfaces. Some 140 protected species – including, currently, a pair of ultra-rare Bonelli's eagles – call the Calanques home. As do 800 types of spider, among them the black widow, whose dangerous (but rarely encountered) presence is a key indicator of the desert-like nature of a place where the thirsty limestone draws all water into itself.
This wealth of fauna helps to explain why Les Calanques has been safeguarded as an area of ecological significance since as far back as 1975. But it was not until April this year that it received the ultimate official rubber stamp as a national park.
This is no small promotion. It becomes just the 10th French parc national. Only seven of these are on the mainland – and the arrival of the Parc National des Calanques is the first such elevation in France proper since the unveiling of the Parc National du Mercantour in the Alps in August 1979.
Not that the route to national status has been straightforward. The GIP (Groupement d'Intérêt Public) des Calanques – the organisation created to see the area through the gestation period – was established in 1999. But it found its efforts repeatedly thwarted by local concerns, not least from fishermen worried at being excluded from the potential park. When I meet him at his office on the outskirts of Marseille, Benjamin Durand, the director of GIP des Calanques, has the air of a man who has been running in circles. "It is an unusual challenge, having a national park so close to a major city," he admits. "This community lives with nature. But if that nature is destroyed, it is bad for the community."
Nearly 20km across from west to east, and more than 500sq km in size (although only 16 per cent of the expanse is on land), the park that was born in April has, by necessity, come to life with a few regulations attached. Fishing is restricted – though only in 10 per cent of the water. Climbing is similarly affected at sites where birds nest. Jet skis are entirely banned and tourist boats slipping around from Marseille can no longer use loudspeakers.
But in general, the park extends an invitation to visitors – especially the walkers who come to push into the dust and descending drama of its peaks, troughs and pathways.
At the Luminy entrance, I keep my rendezvous with Gérard Torossian. A specialist on the Calanques, he belongs to Marseille Provence Greeters – local enthusiasts who are keen to guide outsiders around their city and region. In his late sixties, but wiry and tanned, he is a picture of later-life health, imbued with a fast-striding fitness hard earned over decades of excursions down these trails. And he knows his stuff, pointing out endless varieties of flora as we forge into the midst of the park. He was – he reveals – a butcher, but has now settled into an active retirement, venturing into the Calanques at least twice a week with tourists in tow. Does he miss his old profession? He pauses for a moment. "I like this very much more," he replies, face broadening to a grin.
It is not difficult to understand why. After 30 minutes, we crest a bluff and find ourselves staring down into the thin chasm of Calanque de Morgiou. Here is a postcard image of what makes the park special: a silvery sliver pokes at the land; tiny boats bob delicately on the waves; walls of limestone supply a vertical frame. There are hidden depths too. Its entrance concealed 37m below the water line, and accessible only to divers, the Grotte Cosquer is coated with cave paintings daubed 27,000 years ago.
Glancing around, I am not sure that the landscape has changed. Certainly, there is little but raw stone to GR98, the path that spans the whole west-east width of the park. "Careful, many people fall here," Torossian warns in his heavy Provençal accent, all the while plunging downhill with the sure-footed confidence of a man who knows each pebble. Above, the lofty rock formation of La Grande Candelle looks pale as it jabs at the blue sky.
At the bottom of the slope, Calanque de Sugiton delivers another dose of pristine beauty, the light dancing on its ebb and flow, a quiet beach in its far corner. Torossian pulls out two bottles of water and a packet of biscuits – and we eat our snack in silence amid the fragrant whoosh of pine trees in the wind. Nothing more needs saying.
We turn back at this juncture, partly because the day is lengthening, partly because I want to attack the park from the opposite side. Next morning, I hop on to a train at Marseille-Saint-Charles station for the 40-minute ride to Cassis, the town whose seafront prettiness delineates the eastern limit of the Calanques. And again, the journey deals in contrasts, Marseille's north-easterly districts a patchwork of warehouses and tower blocks, rust and metal, the subsequent countryside a mesh of fields, furrows, olive groves and vineyards.
Cassis has made its name as an elegant resort, but for the intrepid, it is another gateway to the Calanques. Just outside town, I pick up the Sentier du Petit Prince, a well-signed path that abandons the ice-cream parlours as it slices into the wilderness. Not that man is notable by his absence. Calanque de Port-Miou still bears the scars of the mining that was conducted here until 1981. Calanque de Port-Pin, meanwhile, is awash with weekend swimmers. And at Calanque d'En-Vau, a lone yacht enjoys its privacy. Watching it from 120m above, I marvel again that I am scarcely 24km from a city of 1.5 million inhabitants.
Two hours later, I will revisit this trio of inlets via a pleasure cruiser from Cassis – a mini-voyage that offers a different perspective on these gashes in the Gallic underbelly – before succumbing to the lure of Poissonnerie Laurent on the quay. Part fishmonger, part restaurant, it caters to local shoppers as well as Saturday diners – although it is tricky to believe that anyone could reproduce its excellent bouillabaisse fish stew (€35) in their own kitchen.
I polish off this gloopy mixture, because I need the energy. I have one last hike planned – up and away on the other side of Cassis, where the Route des Crêtes coils to the top of the Cap Canaille headland, France's tallest sea cliffs. These ancient behemoths tip the scales at 399m, and the 3km march to the rooftop proves punishing, the sun prodding at my back with every step. But the view is a fine reward – not least because I can see all the way across the Parc National des Calanques to the hulking shadows of Marseille in the distance. I can also see the precise curve of the A50 motorway as it passes tactfully behind the natural miracle in its orbit.
It is a pertinent discovery. For in a country often in thrall to waterfront casinos and palace hotels on crystal bays, here – for a glorious 16km – there is no coast road. Just the unfettered results of what happens when saltwater and limestone are left to uninterrupted confrontation. It may have taken 13 years of bureaucratic slog to enshrine the Calanques as a zone ring-fenced from incursion, but some things are undoubtedly worth waiting for.
British Airways (0844 4930787; ba.com) and easyJet (0843 104 5000; easyjet.com) fly to Marseille daily from Gatwick; Ryanair (0871 2460000; ryanair.com) daily from Stansted.
The 21 bus runs from La Bourse station (22 La Canebière) and takes 45 minutes to the park entrance at Luminy. Single €1.50 (00 33 4 91 91 92 10; rtm.fr).
Trains to Cassis run from Marseille-Saint-Charles station and cost from €11.20 return (00 33 8 92 33 53 35; voyages-sncf.com).
Marseille Provence Greeters (marseilleprovence greeters.com) runs tours with local guides.
Parc National des Calanques: parcs nationaux.fr
Groupement d'Intérêt Public des Calanques: gipcalanques.fr
Cassis tourism: ot-cassis.com
Marseille tourism: marseille-tourisme.com
Visit Provence: visitprovence.com