Joh. Jos. Prüm. My favorite Riesling by far, and an iconic and absolutely traditional producer. I don't know if you need an appointment, but Google seems to think they're open Monday-Friday, 9:00-5:00. Look for the Wehlener Sonnenuhr sundial, which marks their most iconic vineyard. See it in the center of this picture:
Wehlener+Sonnenuhr+Vineyard.jpg
And this more close-up view:
we_su.jpg
Excellent, thanks!
Looks like I am boiling down to staying in Germany for a few days in the Mosel Valley, then maybe basing out of Metz, France.