plane{<0,1,0>,1 hollow  // 
      
      texture{ pigment {color rgb<0.1,0.35,0.8>}
                         finish {ambient 1  diffuse 0}}

      texture{pigment { bozo turbulence 0.65
                        octaves 6  omega 0.7 lambda 2 
                        color_map { [0.0  color rgb <0.95, 0.95, 0.95> ]
                                    [0.2 color rgb <0.85, 0.85, 0.85> ]
                                    [0.5 color rgbt <1, 1, 1, 1>*1.1 ]
                                    [1.0 color rgbt <1, 1, 1, 1>*1.1 ]      }
                        rotate<10,20,0>
                        scale <0.3, 0.4, 0.2> }
              finish {ambient 1 diffuse 0}}
      scale 10000}  
// fog at the horizon     
fog{distance 300000 color White}