In, cough, 1991, my wife and I did a bike tour in Europe for our honeymoon. We spent a total of 4 weeks in Holland, England, and Germany. We took trains and of course ferries to cover larger differences. We did less than 50 miles in a typical day, iirc.

The thing is, back then, no GPS, no Internet, just maps and asking people for help. The trip was not particularly challenging and was very rewarding. It seems like such a trip would be even more easy and fun today with all of the extra context and information that you have with a smart phone.