Located in the north of Spain, the Rioja wine region is named after the province of La Rioja and is split into the three subregions of Rioja Alta, Rioja Baja and Rioja Alavesa.
The vineyards in Rioja are protected from the strong winds of Northern Spain by the Cantabrian Mountains, helping to maintain a continental climate. The reds dominate Rioja, with Tempranillo far and away the most popular grape, Garnarcha is often used too. Most whites from this area are made from Viura.
Rioja classifies it's wines in a very unique way, primarily using oak-aging to differentiate between the four major classifications.
Rioja - Is the most common classification in Rioja and generally produces the cheapest bottles, usually there is little to no oak aging and 1-2 years of total aging.
Crianza - generally good value for money, 1 year of oak aging in used oak which produces less strong oak flavours, allowing the fruity notes to come to the forefront, and then a further 1 year of bottle aging.
Reserva - Have been aged for a minimum of 3 years, with at least one year in casks. These are higher end wines, a happy medium between the fruitfulness of a Crianza, and the oak of a Gran Reserva.
Gran Reserva - as explained by riojawine.com, these are "Selected wines from exceptional vintages which have spent at least 2 years in oak casks and 3 years in the bottle." Expect tannic wines with a lot of Oak.