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There were no signs warning against picking up hitchhikers, no visible fences. Only the 25-foot-tall floodlights rising along the edges hinted that something other than grazing cows lay ahead.Smooth, featureless concrete rose on the horizon like the wall of a dam as I approached; nearly four times as tall as a man, it snaked along the crests of the hills, its top curled toward me as if under pressure.
