What's the old joke about never being lost because everyone tells me where to go?
I would pass up such obvious cycling glamour spots as Wales, Ireland or the south of France, and vote for the Nuremburg area of Germany. I was stationed close by for a year and a half on the Uncle Sam travel plan, and found it to be cycling heaven. Lovely rolling scenery, polite drivers, mucho bike paths and paved shoulders (what a novel concept, build roads to accomodate more than just cars!), towns for rest stops every 5 or 6 miles, cathedrals and museums to visit and a brewery in every town! Not to hot in the summer and sunlight until almost 10 in July. Sigh. Wish I had ridden more.
On the domestic side, I'd take two or three days and ride the coastal roads on the north west shore of Michigan's lower penninsula from Traverse City through Charlevoix, Petoskey, Harbor Springs and Cross Village to Mackinaw in September. Twisty, winding roads past cottages and spectacular lake views, moderate hills covered with flaming red maples, little country stores for snack breaks. Lovely. The annual DALMAC ride (Michigan's RAGRBRAI) finishes on this strech over Labor Day. I'd recommend that ride but the colors are better later.
Tom Adams, Kansas City