Valladolid, in northern Castile, is the hub of a highly productive wine region that for foreigners has always been overshadowed by neighbouring Rioja. For Spaniards, however, it’s a been an enduring love affair, as the much prized Duero wines were regularly quaffed by the Hapsburg kings back in the 16th century. Coursing through Old Castile, the Duero river combines with chalky soil and wildly fluctuating temperatures to nurture some of Spain’s stellar reservas. Rueda (white), Cigales (rosé and red), Toro (red) and the smooth yet potent Ribera (red) all originate here. One of the oldest bodega labels, Vega Sicilia, has been described by a British wine-writer as “on a Wagnerian scale of subtlety and complexity”. Beat that if you can. Altogether there are some 200 bodegas in this part of Castile and no shortage of eponymous castles, as the Duero river was once the frontline between the Christians and the Moors in the lengthy “reconquest”.

The first stop on the wine trail should be Peñafiel, vsible for miles around thanks to its hilltop castle straight out of a fairy-tale. Mirage it isn’t, however, as the 15th century castle now houses the provincial Wine Museum. This is where you learn that wine first came to these shores with the Phoenicians but that it was the Romans who started cultivation in Castile. Some historians maintain that the Moors subsequently ripped out all the vines, yet as they continued to produce and export sherry down south, this is a moot point.

What is certain is that in Peñafiel you are at the centre of the small production area (12,000 hectares) of Ribera del Duero, visible in the vines that stripe the surrounding slopes and chimneys that poke out of the hillside below the castle. The latter are not some form of troglodyte dwelling but ventilation shafts for cellars burrowed into the cool slopes. Backtracking a few kilometres towards Valladolid brings you to Valbuena del Duero and a bodega with a 12th century monastery attached, a relic of the Cistercian monks who brought viticultural expertise from France. At the Matarromera bodega, you can taste and buy some of the Duero’s most prestigious labels including Rento (short for Renacimiento), of which only 16,000 bottles are produced a year, initially priced at around 30 euros a bottle. This is one of the denomination’s great success stories which has helped double the production area since the early 1990s. Strong and fruity, Rento wavers threateningly between 13.5° and 14.5° - but you have to remember that wine produced by the Romans was invariably a knockout 16°-18°. And this is a princely label as the cellar contains casks bearing King Juan Carlos’ name and a horde set aside for Prince Felipe.

Wherever you eat in this area (even at the Valldolid airport bar) you are likely to be served Ribera del Duero as the red wine and, if you choose white, Rueda. Fast becoming Spain’s top white wine, and certainly its most consistent, Rueda is made from the verdejo grape, sometimes mixed with a dash of sauvignon blanc, to give wonderful aromas of apples, pears and fresh grass. The production area lies southwest of Valladolid around Medina del Campo.

Shift 60km due west of Valladolid and you enter the denomination of Castile’s next red wine success story: Toro. Named after a delightful small town which sits high on a ridge overlooking the Duero and plains of Zamora province, this production area (about a third the size of Ribera del Duero) is monopolised by the local grape, tinta de Toro. This tempranillo clone thrives in the gently rolling terrain, enjoying more sunshine and less rain than vineyards further east. The result is a grape-juice that is highly nutritious and dense in colour - before it even enters a barrel. Once aged, it becomes heavy in tannin, acquiring strong balsamic and fruit flavours. Toro’s growing popularity is attracting investment from big-time vintners of Rioja and Ribera del Duero who aim to create an elegant version of Toro’s former rustic self. Already, its most prestigious label, Gran Colegiata, named after a beautiful Romanesque and Gothic church, is highly rated. Could it be the ugly duckling of Castilla-Léon?