PREPARE and bake chocolate cake mix according to package directions using a 9x13-inch cake pan. Cool completely before decorating. Cut a 2-inch strip off the side of the cake to use as boulders.
FROST the rest of the cake with 2 cups Cool Whip Whipped Topping and sprinkle 1 cup of Oreo Baking Crumbs on the top to represent dirt. (You can also cover sides of cake with crumbs to represent dirt too).
PLACE cut up boulders in piles on top of cake and place small clean toy construction vehicles all over the cake.