German Riesling
Germany produces some of the most amazing Riesling in the world. The most famous German region, the Mosel, is famed for its lime, slate and smoky Rieslings, whereas farther down the river the Rheingau and Rheinhessen produce more lush, stone-fruit-driven Riesling. Once you know how German wines are classified, it's easy to select a quality bottle (source: European Wine Exploration Map _ Wine Folly.pdf).
This is the wine of the trip's German leg: the Mosel Valley around Trier, with cellar tastings at Weingut Vereinigte Hospitien and Bischöfliche Weingüter Trier, and Riesling on the Luxembourg bank too (Luxembourg Moselle, the Koeppchen slope at Wormeldange). Wine Folly notes Vinho Verde's whites taste a lot like fine dry Alsatian Riesling — for Alsace's version of the grape, see Alsace Grape Varieties. Germany's northern sparkling-wine country, Freyburg & the Saale-Unstrut (Leißling / Naumburg), is a related Tier-2 detour.