Vinho do Porto

There are four types of Port wine: white, red, ruby and tawny. White Port gets darker with age, whereas the older reds are paler in color. All Ports spend a minimum of a few years maturing in casks before being bottled. Old Ports, those of 10, 20 and 30 years are in fact blends of wines of different ages. The age on the bottle is the average age of the contents, Only vintage Ports mature in the bottle.
Vintages are only declared in certain years when the harvest is condiered by the Port Wine Institute to be of sufficiently high quality. A bottle of vintage Port should be stored away from the light, and on its side to prevent the cork drying out. Once opened vintage Port should be consumed within 48 hours.

My personal favorite is Donna Antonia from Ferreira. In Lisboa you can discover you own favorite at the Instituto do Vinho do Porto at Rua de São Pedro de Alcântara. Alternatively you could take the train to Porto and taste the wines in their home town.