The crushed-rock-and-shell roadbed is straight and flat, running for 12 miles atop the L-40 levy, which separates the Everglades from this stretch of southern Palm Beach County. The dike road, which opened to bikers and hikers last October, connects the Loxahatchee National Wildlife Refuge Visitor Center in the north to the south entrance of the refuge. A slight promontory in an otherwise flat landscape, the levy service road offers an expansive view of the seemingly endless river of grass, which stretches west to the bright blue horizon unchecked in its green sameness, save for a few stands of tall trees. The path, bordered on the east by thick mangroves, also offers close brushes with nature -- and plenty of bone-jarring abuse on the bumpy road. In the canal that curves along the edge of the Everglades just below the road, white egrets wade on gawky legs and dip their bills into the water as they hunt for food, unconcerned about passing bikers. But if you're cruising along at any decent speed, don't survey the scene for too long. The tight-packed dirt road is rife with washboard ripples and large chunks of rock that poke through the surface. This makes for a rough ride and creates the potential for a wipeout even on this benign-looking trail, which is bordered bucolically on either side by wild grasses and yellow and lavender flowers. With absolutely no shade, the road's white rock and sand glare brightly and amplify the heat of the day. This actually seems to be an attraction for the huge dragonflies that bask on the surface and flutter up as bike tires approach, continually flying into riders. Warning: There is no bathroom or potable water along the way.