If you're even mildly adventurous, there is no better way to unlock the secrets of Spain than to head out on the road and follow your nose to the places that entice you most. Dig out tempting tapas bars on old cobbled streets. Watch birds of prey wheeling in plummeting canyons. Dine on freshly caught fish with local wine in small ports. Find your own way to romantic hilltop castles and medieval monasteries nestling in verdant valleys. What you'll run across on the way will probably be just as enchanting.
Away from the big cities and the holiday costas, Spain rarely fails to surprise and please the eyes, be it with the huddled stone houses and red-tile roofs of ancient villages, a set of rolling wooded hills rising from the plains, or a line of cliffs washed by strong Atlantic surf. Nowhere in Spain is untouristed, but it's never hard to get well off the beaten track and make surprising discoveries – especially in the less-travelled north, west and centre of the country.
The northern coastal regions of Galicia, Asturias, Cantabria and the Basque country are sometimes described as "green Spain", which is accurate because this is the rainiest part of the country. But in the most popular travel months, from June to September, you have almost as much chance of sunny days here as you have by the Mediterranean. The greenery extends from high inland mountains right down to a coast that is liberally endowed with dramatic capes and curves of sandy beach.
The so-called central plains – the regions of Castilla y León and Castilla-La Mancha – are drier, but are more rolling than flat and even break out here and there into high mountains and deep canyons. Castilla y León (north and west of Madrid) was the heartland of the medieval kingdom of Castile that laid the foundations of the Spanish nation. Its cities and villages are perhaps most quintessentially Spanish of all.
In the west, bordering Portugal, lies Extremadura, a land of more rolling plains, olive groves, oak forests and surprisingly abrupt mountains rising around its edges, along with villages, towns and cities such as Mérida and Cáceres, that still echo the Middle Ages. It was from here that many Spanish conquistadors hailed, including Francisco Pizarro; moreover cities across the Americas – Albuquerque, Mérida, Medellín – were first founded in Extremadura.
You can fly direct to numerous regional airports from Britain. Among the less visited destinations in northern Spain, easyJet (0843 104 5000; easyJet.com) serves Bilbao, Asturias airport and Santiago de Compostela; Ryanair (0871 246 0000; ryanair.com) flies to Santiago and Santander; and Vueling (0906 754 7541; vueling.com) flies to Bilbao, La Coruña and Vigo.
Alternatively, bring your own car. To avoid the drive through France you can put your vehicle on Brittany Ferries (0871 244 0744; brittany-ferries.co.uk), which sails overnight from Portsmouth to Bilbao and Santander and, from March to October, Plymouth to Santander.
Tour operators also offer some excellent itineraries to show you the road less travelled. Headwater (0845 154 5495; headwater.com) offers seven-night self-guided walking holidays based at the stylish Hotel El Milano Real in Castilla y León's Sierra de Gredos between March and October, from £989 per person including car hire from Madrid airport and most meals.
Alternatively, you could go for a self-catering holiday on an Asturias country estate with Inntravel (01653 617004; inntravel.co.uk), which offers seven nights in a two-bedroom house for two people from £988 including car hire from Asturias airport any time between March and October.
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Hidden beaches of the north
The costas may have warmer waters, but for beauty and lack of crowds, you can't beat the sandy strands on the north coast.
In Cantabria, there's Playa de Sonabia, beneath high crags on a rock-lined inlet near Oriñón. Watch griffon vultures circle above, then enjoy creative tapas at Somera (00 34 94 260 5448), nearby in Laredo.
Playa de Torimbia, left, near Niembro in Asturias, is a golden crescent bounded by rocky headlands and a bowl of green hills. The relaxed La Posada de Babel (00 34 985402525; laposadadebabel.com) in La Pereda, south of Llanes has doubles from €96 including breakfast (closed December to March).
West of Ribadeo in Galicia, the 1.5km-long Praia As Catedrais is named after awesome rock arches. Head down to Praia do Picón at the foot of the Acantilados de Loiba cliffs. Semáforo de Bares (00 34 98 141 7147; hotelsemaforodebares.com) is a former maritime signals station with doubles from €56.
Ebro and beyond
A trip along the remote upper reaches of the Ebro River, above, in Cantabria, takes in rural valley scenery and sites from early Christianity in the form of rock-cut churches, some of which date back to the 7th century.
Start with the multi-arched, two-nave Iglesia Rupestre de Santa María de Valverde (if locked, get the key from the house across the road) 40km south of Reinosa, and don't miss the Centro de Interpretación del Rupestre (00 34 94 277 6146; closed Monday, call ahead for weekday visits mid-September to mid-June).
Some 30km east, Arroyuelos and Presillas de Bricia both accommodate rock-cut churches. Most exciting of all is the wonderfully-sited El Tobazo cave-church, high in the Ebro gorge near Villaescusa del Ebro, which requires a 700m uphill walk past a beautiful waterfall.
Asturias' Parque Natural de Somiedo, above (00 34 98 576 3758; parquenaturalsomiedo.es) has gorgeous mountains, cute stone villages, and you might even glimpse one of Spain's 200 brown bears. The Parque Natural Arribes del Duero (00 34 92 308 2994; patrimonionatural.org), west of Salamanca, has the World-Heritage-listed prehistoric rock carvings of Siega Verde.
Meanwhile, Parque Nacional de las Islas Atlánticas de Galicia (00 34 88 621 8090; iatlanticas.es), has the Cíes Islands which are ideal for swimming and lolling around on beaches. A 45-minute ferry trip leaves from Vigo between June and September.
Camping is the only option on the islands and you'll need a permit from the ferry building in Vigo first (00 34 986 225 272; mardeons.com; €16). Once there, Camping Islas Cíes (00 34 986438358; campingislascies.com) has pitches from €6.30pp.
In north-east Extremadura, between Madrid and the Portuguese border, a series of verdant valleys, dotted with streams and medieval villages, runs down from the Sierra de Gredos .
In La Vera (the Río Tiétar valley), don't miss the Monasterio de Yuste, above (00 34 927172197; patrimonionacional.es; €9), where King Carlos I retired to die in 1557 having overseen the creation of the Spanish empire. The 28km Ruta del Emperador retraces the gouty monarch's final mountainous journey to Yuste.
Cities off the beaten track
The port of La Coruña, perched on a promontory in Spain's north-west (00 34 981 923 093; turismocoruna.com) is historic, cultured, culinary, beachy and festive. The old town holds the grave of the British general immortalised in Charles Wolfe's poem, The Burial of Sir John Moore after Corunna.
León, above (00 34 987 237 082; turismoleon.org), to the north of Spain's central plains, attracts tens of thousands of Camino de Santiago pilgrims but by few others. It has a breathtaking gothic cathedral and its big student population brings the Barrio Húmedo alive with nocturnal revelry.
Capital of the Basque region yet relatively unheard of, Vitoria (00 34 945 16 15 98; vitoria-gasteiz.org) has a charming medieval quarter, a top modern-art museum in Artium (00 34 94 520 9000; artium.org; €6), and great tapas bars, such as Izartza (00 34 94 523 5533; izartza.com) at Plaza Nueva 5.
Rural bolt holes
Deep in green Galicia, the 16th-century manor, Casa de Trillo (00 34 981 727 778; casadetrillo.com), has lovely gardens and cosy B&B doubles from €60. It's also a great base for exploring the Costa da Morte ("Coast of Death").
British-run Posada del Valle, above (00 34 98 584 1157; posadadelvalle.com), in a valley near the spectacular Picos de Europa, has its own organic farm, with workshops and room-only doubles from €66. For more small-hotels and self-catering options: Casas Cantabricas (01223 328721; casas.co.uk).
Trujillo, in Extremadura, is packed with churches and mansions, one of which is now the Posada Dos Orillas (00 34 927 659 079; dosorillas.com). It offers excellent service and rooms in colonial style; doubles without breakfast from €60.