This is the old Rollins Pass/Needle Eye Railway route that was used back in the mid 1800's in Colorado to cross the Continental Divide, reaching altitudes of just shy of 12,000 feet. During the winter months the winds regularly hit hurricane strength and the snow easily can reach 20+ feet. The route was closed once the Moffat Tunnel, which is 6.2 miles long and opened in 1928, eliminated the need for the trains to make this treacherous trek over the mountains. What you see now is the remnants of the rail bed, which is a popular trekking and camping area.