Ok one more if you like the wide open plains:

There is a campground (Crow Valley) at Briggsdale. I've done a three day weekend ride as follows:
- Friday late in day cycle from Fort Collins and camp at Briggsdale
- Saturday ride in search of the WY/CO/NE triple point. There is some gravel road, but nothing too bad. You can make a big square and come back via Grover. Camp at Briggsdale again.
- Sunday return
There is some nice riding out by the Pawnee Buttes.

The other one that takes a slight variation is to ride to the West Pawnee Ranch B&B. A non-cyclist can meet you out at the B&B to stay together before you ride back.

I agree with you there is a certain beauty of the wide open plains. I started an exercise of trying to ride all the roads in Weld County. I printed out a map and started checking them off (~4000 miles of county roads most of them gravel). I got ~20% done before moving from Fort Collins, so eventually will be back to do some more