I had crossed this way one sun-soaked afternoon with my bicycle. I scrambled to the road, down the steep gorge cut into the mountain like a chasm in Doré's Inferno, before the mists descended - the famous Pyrenean mer de nuages, when the peaks protrude above the lakes of cloud like an archipelago. Beautiful from above, miserable to be swamped in, the mist demonstrates that the mountains are as dangerous as they are spectacular. My companions arrived later and were stranded, helpless, for hours in the thickening fog.

We were on the well-trodden refugee route across the passes. Professed Jews expelled by the Spanish Inquisition in 1492, the Mudejares had tramped in 1502 over the stern mountain barrier to markets less picky about the traders' religion. There was illicit commercial traffic, too. On the narrow crest of the Port de Salau, near the ski slopes of Guzet-Neige, high above where the grass hairpins peter out into sheep tracks, stand the ruins of a sizeable customs post and warehouse for seized contraband.

The frontier follows the chain's main crests, from the low verdant hills of Basque territory in the west where Lammergeier vultures fly, over the mighty bare-rock passes of the 3,000m-high central massif and the stupendous snow-tipped amphitheatre cliffs of the Cirques de Lescun and Gavarnie.

This is ripe smuggling country. The Basques were famous contrebandiers, padding the mountain tracks in their espadrilles, with waxclothed bales of Lyon silk, caskets of silver chains, beads, watches down to nocturnal punts across the Bidassoa river, dodging the patrols, to the receiving houses in Spanish Basque territory. Contraband meant more than money: it was a defiant act of liberty. Overrun so many times - Romans, Goths, Vandals, Visigoths, Moors, Gascons, English - the Pyrenean mountain people have a deep and atavistic sense of identity begrudging any wider patriotism. They tend to say: "Town first, region second, but France? If you insist."

In the west the range gradually dips through the gorgeous rustic wilds, forests and ravines, of the Couserans in a long seaward descent to the vineyards of the Roussillon and the Vermilion Coast. The Spanish poet Antonio Machado fled here, to the fishing-village of Collioure, from Barcelona, in the wretched, footsore exodus of Republicans, after the city fell to Franco's armies. "I have walked many roads," he wrote, "and opened many new paths ... everywhere I have seen caravans of sadness, proud men, beaten men, in the dark shadows, bewildered."

Today some drive the Pyrenees - motorcyclists get a special welcome at a hotel on the Col de Peyresourde - others walk, some along the ancient Route des Crêtes followed by pilgrims to Saint James's shrine in Compostela. For cyclists there is the Raid Pyrénéen - the "Pyrenean hard ride". This runs from Hendaye, an unlovely border town with splendid surf beaches on the Atlantic, to Cerbère, a pretty fishing cove above Catalonia: 18 cols, 720km in no more than four and a half days.

Inaugurated in 1951 by a local cycle club, the Raid mirrors the epic of the early Tour de France. From 1910 to the mid-1920s, Tour riders crossed the entire Pyrenean chain in two massive stages: 326km and 323km. They called the daunting cols of the middle section, prowled by bears, the Circle of Death. Even the fearless Gascons called one col road - the shortcut to market in the next valley - Tourmalet, "a bad detour". This col, at 2,114m, marks the apex of the Raid and a distinct cultural shift: from proud Basque with their pelote, tugs-o-war, fandango, dried red peppers and unfathomable language, to the gentler dances, songs and attitudes of south-western France, the Languedoc, or Occitane.

The Occitanes said "oc" for "yes", their language closely related to the lyric tongue of the Provençal troubadours, also to Catalan, which Franco banned. Similarly, the sunkissed southern French, ever despised and mistrusted by the frosty northerners, the powerbrokers in Paris, who said "oy", lost out. But, along the eastern Pyrenees, you'll hear the "oc" on market days, in bars, town squares, at village fêtes when they sing.

The agriculture is as ancient as the songs. Herdsmen and shepherds still tend sheep and cattle on the high pasturage all summer, wary of bears (recently reintroduced), wolves, harsh weather. In the Second World War, such men acted as "passeurs", guiding Allied airmen and young Frenchmen evading forced labour across the mountains into neutral Spain. Many of them were caught and delivered to the Gestapo. For today's traveller, the journey across the Pyrenees has many charms, not least in the glorious changing folds of landscape, the patterns of life - the de luxe of the spas, the bucolic rhythm of the remote villages. And, like the people who inhabit them, the mountains refuse to conform. They are, by turns, rumpled, jagged, long petrified spines, huge cones, mighty shield bosses and their valleys, sumptuous cascades of variables of green leaf and moss and lea. Any adventure in these most beautiful and forbidding mountains is tough and exhilarating. Riding them, we marvel at their power to deter and to inspire, and laugh like kids on the last downhill, away from them to the sea.

Graeme Fife is the author of 'The Terror: the Shadow of the Guillotine, France 1792-94' (Piatkus, £9.99) and 'Tour de France: the History, the Legend, the Riders' (Mainstream, £9.99)

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How to get there

British Airways (0870-850 9850; www.ba.com) and easyJet (0905-821 0905; www.easyjet.com) offer flights to Toulouse from £100 return. Ryanair (0906-270 5656; www.ryanair.com) offers return flights from London and Liverpool to Carcassonne from £80.

Graeme Fife travelled to the area with Bike Pyrenees (00 33 5 61 04 90 61; www.bikepyrenees.com), which offers a fully supported nine-night Raid tour for €1,200 (£857) per person, based on two sharing, including transfers, b&b and dinner. Dates for 2006 are 8 and 22 June, 31 August and 22 September.