Madeira is produced on the Portuguese island of Madeira in the Atlantic and is one of the world's most unique and durable wines. It is fortified with neutral grape spirit (for most styles during fermentation, giving sweetness) and undergoes deliberate heat treatment — estufagem — which mimics the history of extreme heat that old wines were exposed to on board ships.

Styles by grape variety

Sercial: Dry, high acidity, pale, nutty and citrus. Served chilled as an aperitif.
Verdelho: Off-dry, smoky and stone fruit.
Bual (Boal): Medium-sweet, rich nutty-caramel.
Malvasia (Malmsey): Sweet, darkest, honey and dried fruit.

Estufagem

Wine is stored in heated vessels (estufa) at 45–50 °C for at least 90 days, or in wood (canteiro method) under rooftops, naturally warmed by solar heat for years. Heat caramelises and oxidises the wine, giving the characteristic tangy-nutty rancio character.

Madeira, thanks to its extreme oxidation and acidity, can age for hundreds of years.