Heart of Iowa Nature Trail - A Super quiet trail
I rode theHeart of Iowa Nature Trail from Slater to Cambridge in July 2017.
The Signage in Huxley is a little bit sparse. There were a few places where my bike went a bit squirrelly, but it was mostly smooth sailing when I went ~14mph.
Had to de-bike before Huxley and walk gravel to the road because I didn't want to risk getting a flat or crashing. If you had a wider wheelbase, you'd be fine. There was literally no one else out on the trail.
In Huxley the trail has an OGFC asphalt overlay (although there is fine gravel on top) between 5th and US 69. They also paved (concrete) in between US 69 and 560th Ave.
Wheel Size: 28mm road bike