Castilla y Leon, in the northern half of the central Iberian Plateau, is the largest of Spain's 17 administrative regions. It accounts for about one-fifth of the country's total surface area and stretches roughly 220 miles (355km) from the centre of Spain almost all the way to the north coast. Equally wide, it connects its famous neighbor Rioja with the border of Portugal.
Although the region's economy has traditionally focused on cereal crops, viticulture has been a significant economic activity in Castilla y Leon for more than two thousand years. In the late 20th and early 21st centuries, the acreage devoted to vineyards fell significantly, and the focus was shifted from quantity to quality. Today, Castilla y Leon produces some of Spain's most respected wines, most notably those of the Ribera del Duero, Toro, Rueda and Bierzo areas.
Castilla y Leon came into administrative existence in 1983, when the two historical provinces of Leon and Castilla la Vieja were unified. The region is the heartland around which the modern Spanish state was formed; Madrid (the national capital) was once part of Castilla la Vieja. But Castilla y Leon is not just of interest in modern and political contexts; its rich cultural history dates back more than two thousand years, as manifested by its six UNESCO world heritage sites. These include the medieval city walls of Avila, the Roman Aqueduct in Segovia, and Atapuerca, an archaeological site rich in Bronze Age and Stone Age artifacts. It has been suggested that wine production in the region pre-dates even the Roman occupation, which began in the first century B.C.
The climate in Castilla y Leon has a remarkably strong continental feel, given how close it comes to the Atlantic Ocean. Hot, dry summers here are followed by sharp, cold winters, when temperatures regularly drop well below freezing. Diurnal temperature shifts are equally pronounced, and play a vital part in the local wine styles; cool nights refresh the vineyards after long, hot days. The region is deprived of any maritime influence by the Cordillera Cantábrica, the mountain range that separates it from the Bay of Biscay. On the other side of these mountains lie the Asturias, Cantabria and Pais Vasco regions, whose cool, fresh climates and fertile hills are in stark contrast to the warm, dry table lands of Castilla y Leon.
Wedged between the Cordillera Cantábrica and the Sistema Central mountains, Castilla y Leon occupies a vast plateau about 125 miles (200km) across and between 2300ft and 3300ft (700m–1000m) above sea-level. Naturally, given this location and the low rainfall, soils here are typically thin and poor. They do become richer in minerals and clays, however, near the region's rivers, of which there are many. The most famous is the Duero, which flows on to become Portugal's Douro. It is in the valley of this famous river that Castilla y Leon's finest vineyard areas are found.
Of Castilla y Leon's nine DO wine zones, all but one surround rivers which ultimately flow into the Duero, and it is no co-incidence that the region's most respected wine districts (Toro, Rueda and of course Ribera del Duero) are those located right in the Duero Valley. The exception here is Bierzo, in the far-northwest of the region, where both the climate and the wines are more closely aligned with those of neighboring Galicia.
Red wines rule in Castilla y Leon, and of the red-wine grapes, Tempranillo (known here by various synonyms including Tinta del Pais, Tinto de Toro and Tinto Fino) is unquestionably the king. It is the grape behind all of the region's finest wines except Bierzo, which makes good use of Mencia. Castilla y Leon's white wines – far fewer in number than the reds, but only marginally less prestigious – are made mostly from Verdejo and Viura.
The international success of key Spanish producers in Castilla y Leon has done much to raise the region's profile. Vega Sicilia, Numanthia-Termes, Campo Eliseo and Bodega Palacios Remondo, among others, have spearheaded modernization in the region and brought renewed interest to its wines.