The Díaz Bayo family is the owner of the Díaz Bayo winery, in Fuentelcésped, Burgos, in the stream of the Duero river. The family has been working in the wine business since 1607, and they own another winery in Rueda, Valladolid, Nuestro de Díaz Bayo. They make elegant wines with the red grape Tempranillo. The oenologist of Díaz Bayo is Isaac Fernandez Montaña, Mariano García´s nephew, the founder of among others the winery Mauro, where Isaac started his professional career, in Castille and Leon. The Díaz Bayo winery makes among others the wines Díaz Bayo 4U, Díaz Bayo 15 Months and Díaz Bayo 20 Months, under the Appellation of Origin Ribera del Duero. The winery belongs to Premium Fincas.