Fermentation and fortification are only the beginning of the process of making Port wine. They must always be followed by a period of ageing, which will allow the wine to mellow and its flavours to develop and mature. Although much Port is now aged in the Douro Valley, Croft and other traditional Port houses prefer to mature their wines in their cool dark lodges at Oporto where the temperate climate of the coast ensures that they will age slowly and harmoniously. One of the unique properties of Port is its ability to gain in richness and flavour over very long periods of ageing in wood. This is partly because it is fortified and partly because it is a wine of extraordinary concentration and aromatic potential.