Portuguese for "stove," estufa refers to the hothouses where Madeira is made. Heated tanks or stoves are used to mimic the beneficial effects of heat-induced maturation that once took place on Madeira wines stored in the sweltering holds of 17th century ships bound for the Americas. The use of the heating process—called estufaguem—virtually ensures that Madeira is almost indestructible and will remain in perfect condition for many decades, even centuries.