dão is a portuguese wine region situated in the região demarcada do dão with the dão-lafões sub region of the centro, portugal. it is one of the oldest established wine regions in portugal. dão wine is produced in a mountainous region with a temperate climate, in the area of the rio mondego and dão rivers in the north central region of portugal. the region became a "denominação de origem controlada" (doc) appellation in 1990. the dão region is the origin of the touriga nacional vine that is the principal component of port wine.