I used a simple moist vanilla cake recipe with buttercream frosting covered with fondant. The black fondant was shaped into cobblestone pattern using an acrylic roller sheet. I made one 11x15 cake and cut it into thirds, frosted each layer and stacked them before carving out the half pipe. I used Charm City cakes edible images and rocks. the entire halp pipe is set on top of a 9x13 cake made of chocolate cake with chocolate ganache filling. The grey/white was also rolled with an acrylic cobblestone pattern.