Last June, I rode the Heart of Iowa Nature Trail from Slater to Rhodes, Iowa. The trail was a mix of pavement, crushed limestone, road, gravel and GRASS (which was quite unexpected).
LENGTH: 30.41 MI
ELEVATION: 472 FT. CLIMBING
TYPE: ASPHALT, CONCRETE, ROAD, GRAVEL, GRASS
View a portion of this trail on Alltrails here. Here is the route on Strava.