Kelly Flats 4x4 Road definitely meets the definition of rough and rugged, it is one of the more difficult trails in northern Colorado. The flats are unnerving for beginners and even the experts have to bypass on some of the obstacles. Would suggest not attempting unless expert at rockcrawling and that type of terrain and also have a highly modified vehicles for rockcrawling and boulders. At the flats you will reach elevations of a little under 9,000 feet and the trail will take you about 3 hours to complete even though it is only 10.7 miles long. Side Note: Kelly Flats is the only 4x4 trail that intersects directly with the Poudre Canyon Highway.