This is the largest cake I've made yet - four 16" round cakes (12 boxes of cake mix). The sides are covered in stripes of white fondant, then we cut squares from black fondant and placed over top. The hill is made from rice krispie treats; I refrigerated the hill to stiffen it up then carved out the tunnel; covered it in icing, then coated the entire hill with brown sugar. The road, rocks and cactus are all made from fondant. The Happy Birthday logo is printed on an edible frosting sheet. I piped the grass in buttercream icing using a grass decorating tip. The cars and ?4? candle are the only non-edible pieces on the cake.