West of Nederland, the Caribou Flats Road (FS505) is an 11 mile route open to ATV riding. Except for spring mud and a steep grade near Eldora, this is a fairly easy route. It passes the Caribou Townsite.
To reach the southern trailhead, head to Eldora. The trailhead is located at the eastern end of Washington Avenue. Once you get to Eldora stay straight and take the dirt road to the Hotel and turn right. Take another right and take a small road between a house and a garage (Yes, thats a public road).
The northern trailhead is off of CR 166J 1 mi from the Rainbow Lakes Campground.
Note: Colorado residents must register their off-highway vehicle with the Colorado State Parks (303) 866-3437. Out-of-state residents who bring OHVs into Colorado must purchase a Colorado Non-Resident OHV permit which is valid from the date of purchase through the following March 31. These permits can be purchased anywhere you get your hunting/fishing licenses in All off-highway vehicles must have an approved muffler and spark arrester. These requirements are subject to change so make sure to contact the Colorado State Parks prior to using your off-highway vehicle.
Note: As of September 2007, ATV riding on Forest Service roads is only permited on roads marked as open to ATV. All ATVs must be registered.
Overall, Caribou Flats Road is the 32nd most popular ATV riding trail of all 90 ATV trails in Colorado.