I call it my Mercedes MLC (Mid Life Crisis). If you squint, the second-hand convertible has the sleek lines of a compact silver Batmobile. It was bought on the promise of rolling away the years, but on London's roads it has had precisely the opposite effect. Every hump, bump and pothole judders up through the hard suspension, reminding me of creaking joints and sclerotic tissue. We need open roads, big views and heart-stopping hairpin bends. So we are going to northern Spain on a man-and-machine honeymoon.
The 24-hour ferry from Portsmouth to Santander takes the strain out of getting to Spain. The Bay of Biscay, renowned for its tantrums, is a waveless sea on this passage: we roll as smooth as a mist into Santander. The balmy temperature is an invitation to have the retractable top of the car down before we have cleared customs. On the autovia, with the wind in my hair, I am starting to enjoy my crisis.
The obvious thing to be said about my first stopover, Santillana del Mar, is that there is no "mar". The sea is a few kilometres away and visitors get a weary look of disapproval if they ask the way to the beach. Despite the absence of buckets and spades, Santillana is popular; it is simply too cute not to attract the coach parties.
The medieval old town is essentially a tale of two plazas – one civic, the other churchy – and a couple of lanes, both of which are all but swamped by hotels, souvenir emporia, restaurants and bars. The Parador Gil Blas, where I am staying, occupies a prime position between the two main drags. Like many paradors it is a historic building – in this instance a grand old family mansion – and has the requisites of manorial living, including suits of armour, portraits of dusty ancestors and antique furniture.
It is not, however, Santillana's history but its prehistory that put it on the map. The cave paintings of Altamira, less than 3km away, were discovered by a 12-year-old girl in 1879. The dozens of murals of bison, horses and deer were not only the first to come to light but some argue that they are also the finest extant examples of Paleolithic art. Some of the daubs are reckoned to be more than 25,000 years old.
Over the years people came in such numbers that their breath and the resulting humidity began to damage the paintings – and the cave is now off limits to the public. There is nevertheless a very engaging museum at the site, with a replica cave that it is claimed "recreates the textures, contours and colour variations of the original cave down to the last millimetre". The replica is revelatory – you can see how the ancient painters used the rocky undulations of the cave ceiling to render their animals in bas relief. Impressive though it is, the "Neocave" can never be the real thing. Tantalisingly, the original cave is just 300m away.
Looking for authenticity I scour the hillside for the entrance of the bona fide Altamira. I walk past it twice before a security guard points me to a clump of trees around a hollow in the meadow to my right. A blue tarpaulin weighted with stones is flapping on the ground just above a small barred iron door hinged from a rough concrete wall set into some rocks. It looks improvised, unfinished. Behind that door lies a space that is often referred to as the "Sistine Chapel of Prehistory". It looks more like the tradesmen's entrance of a nuclear bunker.
Determined to give the car a workout on the way to my next stop, I scorn the autovia route that my dull-witted satnav has selected. I head south along the Valle de Toranzo and then cut east across the Cordillera Cantabrica. The route along the Valle de Pas may not be as grand as the Picos de Europa further west, but the valleys are green and vivid.
The sun is up, the hood is down and we are motoring. The car charges along the hillsides like an eager dog finally unleashed at the park. We attack the hairpins up to the pass at Las Nieves as if chasing rabbits. Wild horses and waterfalls pass in a thrilling blur of motion. Picó* Blanco (1,529m) is off to the left as the plateau opens up; the horizons become larger and the engine note settles to a low growl.
When I get to Argomaniz in the Spanish Basque country, the sunset panorama has an ominous shadow in the east. From the terrace bar I watch hypnotised as a gathering army musters in the sky over the giant plain, flashing blades of lightning. It is clear the assault cannot be long in coming. The bar staff seem unconcerned. I retreat indoors as the wind rises, to avoid being clobbered by the furniture. The staff come running when the storm has reached its full destructive force but it is too late. The rain is whipping in. The wind is lifting the sunshades with their weighted bases into the air and tossing them around like beach balls. One of the shades comes down so hard the heavy granite base shatters.
The drama has passed in the morning. I take the low road east to Sos del Rey Católico in Aragon. The medieval hilltop town lies between Pamplona and Zaragoza and takes its name from Fernando II, the king (rey) who was born here. From a distance it looks untouched by the passing centuries; the gigantic wind turbines that bristle along the spine of the Peña Montañesa range behind the town are the only telltale signs of our times.
Sos is a delight; higgledy-cobbledy streets and beetling alleyways that wind, twist and double back on each other like an intricate Celtic knot. The 12th-century church of San Esteban contains the font in which Fernando II was baptised; the 11th-century crypt underneath is worth a look for its peeling but moving frescoes. The whole multi-storey edifice seems to grow organically out of the hill. At the very top is the keep tower – all that remains of a 10th-century fortress that once held the Christian line against the Moors.
Paradoxically, in this historic town, the parador is a modern building, but one designed to blend in with its neighbours. Every room or terrace has commanding views over the surrounding countryside or the tumbling terracotta roofs of the town.
Manager Emilio Marquez's enthusiasm is so infectious that he talks me into attending a "Los Beatles" themed evening he has initiated. I ask if there is a local Beatles connection, but no, Emilio cheerfully informs me there is none. A local tribute band performs on a rooftop terrace – recalling the Fab Four's last gig on the roof of their offices in Savile Row. There the similarities end. Layers of strangeness accumulate when keener members of the audience sing along to "I am the Walrus" through accents you could slice chorizo with. The opaque lyric "Yellow matter custard, dripping from a dead dog's eye" echoes joyfully along the ancient walls and bounces on to the wide open plains of northern Spain. Señor Lennon would surely approve.
Dinner in the paradors tends towards the hearty and traditional – the cold almond soup here is a palpable hit. La Cocina del Principal restaurant in town is another success. It is accessed by steps down from the street into a cellar, but a door leads to a terrace with a glorious view. The owners make it clear they think I am a mad dog when I insist on having my lunch out in the midday sun. They try to save me from my folly but relent eventually and serve an excellent chuleta de buey (ox T-bone) al fresco. The massive hunk of meat is served almost raw, its dull red hue and yellowing fat signifying a decent period of ageing. An ice-cold beer offsets the raging sun. Swifts and house martins dart about. Almond, olive and cypress trees decorate the hills, their greenery boldly interrupted by gold fields of swirling corn that follow the contours of the land.
On the road again I point the car due north at the great wall of the Pyrenees. The approach is gradual up the Valle de Roncal. The valley narrows to a canyon just north of Sigüés. A thin ribbon of blue delineates the sky and against the light I make out the silhouettes of giant wings. Griffon vultures nest on the steep cliffs and during the day they patrol the valley searching for dead things.
Shortly after the viewpoint at Portillo de Lazar there is a fork in the road; the sign pointing right indicates that France is just 11km away over the high pass at Puerto de Larrau. On impulse I swing right. The clear lines of sight on the mountain road give ample warning of oncoming traffic – and there is very little anyway. I put my foot down and the car comes to life, devouring the Tarmac with an angry roar. Into the hairpins, braking late and powering out of the corners, I can feel the low-profile tyres gripping the road confidently.
The road becomes increasingly precipitous, and as I head up to the 1,500m pass I can only see clouds up ahead. I am forced to a crawl when I drive into the mist and visibility drops alarmingly. Suddenly I feel very small and vulnerable out in the open on the dark mountain. But within minutes the gloom begins to lift and the mist starts to dance with light.
When it lifts a new world of wonders is revealed. I am above the clouds. Torrents of vapour are drifting over the ridges and cascading between spurs into the valleys far below. I am suspended above France and Spain. No longer driving, but flying in my silver machine.
Sankha Guha travelled with Brittany Ferries (0871 244 1400; brittanyferries.com) which sails from Portsmouth and Plymouth to Santander from £209 per person, based on two people travelling together with a car. You can also travel to neighbouring Bilbao from Portsmouth.
Parador Gil Blas, Santillana del Mar (00 34 942 02 80 28; www.parador.es). Doubles start at €176 (£141), room only.
Parador de Argómaniz, Álava (00 34 945 29 32 00; www.parador.es).
Doubles from €158 (£127), room only. Parador de Sos del Rey Católico (00 34 948 88 80 11; www.parador.es). Doubles from €135 (£108), room only.
La Cocina del Principal, Sos del Rey Católico (00 34 948 888348; lacocinadelprincipal.es).
Spanish Tourism Board: spain.info