Mature means the wine has evolved from its youthful style into a just-as-interesting aged style. This can be after 5 years, or after 10, or 50, depending on the wine.
If you've not "done it" before, start with Riesling, Petite Arvine, Gamay, Syrah or Chardonnay as they age in a most accessible manner.
Graacher Domprobst Riesling Beerenauslese Weingut Phillips-Eckstein
Graacher Domprobst Riesling Eiswein Weingut Phillips-Eckstein
Graacher Domprobst Riesling Auslese Weingut Phillips-Eckstein
Grauschiefer Trocken Weingut Phillips-EcksteinA dry Riesling from the steep slate vineyards around Graach. A dash of lemon on hot slate.