The most revered and collectable Port in the world, Quinta do Noval Nacional is a Vintage Port produced from a single 2.5-hectare parcel of ungrafted vines in the Quinta do Noval estate, right next to the cellars. This patch of vines consistently produces a sublime and unique wine which is widely considered to be the pinnacle of Vintage Port and indeed, one of the great wines of the world. It is also almost certainly the rarest of the great wines of the world as so little is released and then, only in the appropriate years.
The Nacional plot is not named after the grape Touriga Nacional (as is commonly assumed). In fact, the site is planted with a range of the best Port varieties including Touriga Nacional (which only accounts for roughly 30%), Touriga Francesa, Tinto Cão (about 20%, 60-year-old vines), Tinta Roriz and some Sousão. The average age of the vines is around 50 years. The wine is called Nacional (i.e. national) because it is produced exclusively from ungrafted vines (i.e. vines on their original rootstocks and therefore directly in touch with the soil of the nation). The yields of these vines are minuscule (around 15 hl/ha) and the tight bunches of small, deeply coloured grapes produce a massively profound, yet typically sublimely refined Port of rare finesse. The La Romanée-Conti of Ports if you like.