The noble rot.
Jurançon acquired its celebrity while being used for the baptism of King Henri IV. The vines grow on steep slopes such as in Hermitage, undergoing both oceanic and mountainous climates. The vine growers use traditional grapes such as Lauzet, Petit and Grand Mansengs and Courbu.
Sweet Jurançon is a golden wine with exotic fruits and honey aromas. It can age for a very long time. REF: Wikipedia