This route follows the Cedar Valley Nature Trail which is a bike path that cuts through the countryside of Eastern Iowa.
http://cedarvalleynaturetrail.com/ : 68 mile route between Ely and Evansdale, Iowa.
This is an iconic and historic trail that once was a railroad route. I think the fact that it is so well known gives this route a lot of appeal. It goes through Cedar Rapids which is a major city. After running it I heard a lot of people say they had done part of the trail or had biked the whole thing. As far as I know, no one has run it all.
The cities it passed through are Cedar Rapids, Hiawatha, Center Point, Urbana, Brandon, La Porte City, and Gilbertville. Coming from Ely, the trail is paved until you exit Center Point and then it turns to crushed limestone before eventually going back to paved around La Porte City. The finish of this route is a pedestrian bridge that spans the Cedar River.
