Rioja is the best known wine-producing region in Spain, situated towards the north of the country and producing mostly red and a small amount of white wines. The name 'Rioja' comes from the local river, the 'Rio Oja ', a tributary of the River Ebro. The region can be divided into three distinct sub-regions - namely Rioja Alta, Rioja Alavesa and Rioja Baja. The region's best wines tend to come from the Limestone-Clay slopes of the Alta and Alavesa, where Tempranillo performs particularly well.Seven grape varieties are permitted in the production of Rioja. Red wines can be made from Tempranillo, Garnacha, Carinena and Graciano, although in practice, most are a blend of Tempranillo and Garnacha with Carinena and Graciano playing a much more minor role. The seventh variety is Cabernet Sauvignon, which is allowed by special dispensation in specific vineyards of one individual producer. White wines are made mostly from Viura and Malvasia.