The wine region of Ribera del Duero is located in Castilla Leon (old Castilla). The wine region spreads in 4 different provinces, though most of the vineyards are located in Burgos, near the town of Aranda de Duero. The 4 provinces are Valladolid (capital of Castilla Leon), Burgos, Soria, and Segovia. Burgos holds most of the vineyard, followed by Valladolid. Both Soria and Segovia hold a small proportion of total vineyard surface. 

There are 2 main factors that explain why Ribera del Duero produces such fantastic red wines.

Soil structure is the first one. Medieval monks were not aware of the geology behind the secret for local wines, but they planted grapes in the monasteries along the river Duero. Recent analyses have outlined a soil perfect for red wine growing: the bedrock is similar to the ones found in the best areas of Priorat or in the west of the Duoro port Valley. Above the bedrock lies a carbonate sub-soil rich in gypsum and at the high-level active chalk is present. 

The second factor is the altitude. Vines are planted between 750 and 850 meters of height. The vineyards occupy both sides of the Duero River. At this height, summers temperatures get as high as 40°C during the day (104°F) but they can sharply fall at night by 25°C or more. This dramatic change in temperature is actually the best thing that can happen to the local grapes. The plants “sleep at night” when temperatures drop. The plants do not consume nutrients from the soil at night. But when the daylight arrives those nutrients remain intact and the plant passes them to the grapes!