The Dao forms an isolated enclave in central Portugal, largely surrounded by mountains and well watered by a network of rivers flowing into the Mondego at the center. It is named after the Dao river which lies entirely within the area.
The focus of the region has always been the commercial center at Viseu. The highest parts of the zone reach 6,000 feet, but the best grape producing land is between 600 and 1,500 feet. Expansion of the vineyards frequently requires the blasting of extensive granite.
Protection of the Dao wines dates back to the twelfth century. Presently administered by the Federation of Vinicultures of the Dao, to obtain the Seal of Origin, the wines must pass tests for quality and content. Red wines must be aged for at least 18 months, but are usually held two to three years before bottling. Only 35% of the entire region’s production can be marketed under the Dao classification, forcing the highest quality.
A profusion of vines are grown. Red wine grapes include Touriga Nacional (minimum 20% required in all Dao reds), Alfrocheiro Preto, Tinta Pinheira, Jaen, Bastardo, and Tinta Roriz (Rioja’s Tempranillo). White wines generally include Arinto do Dao, Borrado das Moscas, Cercal, Barcelo, Encruzado, and Verdelho.