Rioja is northern Spain's most famous wine region, divided into the subregions of Rioja Alta, where most of the top wineries are located; Rioja Alavesa; and Rioja Oriental. The vast majority of Rioja's production is red wine made primarily from the native Tempranillo grape, often blended with Garnacha, Mazuelo (aka Carignan), and Graciano. Traditionally, Rioja reds are categorized as either Crianza, Reserva, or Grand Reserva, representing (in that order) increasing time spent aging in barrel and bottle before release. The whites, usually made from Viura (aka Macabeo) grapes, are also sometimes aged in oak.