Spain is the third largest wine producing country in the world and whose dominant feature is the vast plateau known as the Meseta Central that covers much of central Spain. Several of Spain’s principal rivers that are at the heart of many Spanish wine regions flow to the sea from that central area. These include the eastward flowing Ebro river that runs through the Rioja and several Catalan wine regions and the Duero which flows westward through Ribera del Duero. More than 400 grape vaieties are grown in Spain, but the top 20 account for more than 80% of total production. Key red varieties include Tempranillo, Bobal, Garnacha and Monastrell, while the main white varieties are Airen, Viura/Macabeo and Palomino and Albarino. Spanish wines are often labeled according to the amount of aging the wine has received, with the youngest being called Tinto or Joven. Crianza, Reserva and Gran Reserva indicate increasingly longer aging periods in barrel and bottle prior to release.