Visitors and residents of Colorado often forget that nearly half the state is relatively flat and open.  So why would mountain bikers care about the vast Eastern prairies?  Well, one tiny gem comes to mind: The Pawnee National Grasslands.  "Tiny" at nearly 200,000 acres, Pawnee, in northeast Colorado, is a vast sea of grass and sky once home to the state's pioneering families.  However, rough times during the Depression and Dust Bowl days left the fields abandoned to the area's many birds and antelope.  Pawnee offers bikers many miles of peaceful county roads while the higher mountain trails are locked in winter ice.  Warning: eastern Colorado is notorious for its cacti and goat-head thorns, so bikers must be prepared to deal with likely tire punctures.