I was only in Frankfurt for about 40 minutes, and all I saw was the inside of the train station, but I liked it, and here's why:

THAT, my friends, is herringbrocken. (I think I spelled that right) And there were several other fishy sammiches that looked equally good but that I didn't get a chance to try. Frankfurt is a good crossroads kind of city, so far as train travel goes, so I will make a note to route through it when practical, and maybe even stay a night rather than in Brussels, which objectively sucked.