I'm clearly awesome at making posts when I intend to. So, the abridged version of the rest of my trip. (If you're too young to know what abridged means, it means tl;dr. Heh.) I guess I'll do this in chunks.
Day two in Frankfurt began with us hopping back to the airport to buy Frankfurt Cards (for less than the cost of a normal all-day fare, you get an all-day fare AND a slew of discounts to touristy things) and hop the S-Bahn into town to track down a place for breakfast. We eventually discovered that its name had changed. We wound up getting "Swiss breakfasts" which seem to translate to eggs, a tomato, and a lot of cheese. From there we meandered in the direction of a yarn store (according to Google Maps -- it was correct), walked by a weird-glass-roofed mall called the Zeit Galerie, got refreshments inside in tortured German, and then hopped the U-Bahn over to the Palmengarten where Robin proceeded to take a nap on a lawn chair while I wandered around. We caught dinner at something called 12 Aposteln (tasty, though we both forgot about apple cider, which is apparently Frankfurt's claim to fame, or something like that) and, having successfully burnt a day, went back to crash.
The next day (5/13) saw us heading into nearby Kelsterbach to pick up a rental car (Mercedes A160 hatchback; easily the most anemic thing I've ever driven) and get lost trying to find someplace to nab breakfast (when everything is in German, it's hard to tell what's what) before giving up and deciding to press northward. We'd heard about something called the Märchenstraße and figured we'd roughly follow it northward. Passing through a couple of the places on the way without seeing anything interesting, we wound up in Fulda, where we drove by a restaurant recommendation that was closed, bought buns and cake in a little town market by pointing and waving, and visited the Dom before backtracking to the restaurant (with more associated hand waving and mispronunciation; in the rural bits English is pretty rare) and then heading north to Marburg for the night.
That's enough for now. I'm having enough trouble figuring out how to condense stuff further.