The cellars below the port houses in Vila Nova da Gaia are filled with vats, barrels, casks, bottles and other glass containers of various sizes… all filled with port wine in different stages of the ageing process.

When a young wine arrives from the quinta, the master blender tastes it and decides what kind of port it is destined to be. This determines which containers are used for the ageing process.

Ruby ports are put in the very large wooden vats. These have a smaller surface area-to-volume ratio, so there is less oxidation (Inevitably, some air gets through the sides of the barrel and comes in contact with the wine). By reducing oxidation, the wine keeps its bright red colour and fruity taste.

Other ports, destined for wines with mahogany hues and complex tastes go into the smaller casks where there is more oxidation. The wines do not just sit in the same cask, however. The master blenders and apprentices taste the wines regularly to see what effect time is having. Often they use a glass tube called a wine thief to sample port from a barrel.

Port may be aged for only a few years. Generally speaking Ruby and white ports are served younger than the others. The other ports may be held for six years or more, partly in casks, partly in bottles. Vintage wines and single quinta Vintages may lie for generations before they reach their ideal state.

Some of the wine in the cellars is ancient. It has been lying since Queen Victoria was on the throne of England or since Napoleon's army was defeated at the Battle of Waterloo!