Many artifacts have been discovered at the Cahokia Mounds. These artifacts include pottery, tools, stones, shells, knives, arrowheads, and tattoo kits. Many games have been found as well, including rings, hoops, and pins. Even dice and gambling games have been found as well. Marine shells from the Gulf of Mexico and the Atlantic Ocean have been discovered. Also common are rocks and minerals from all over the United States, including the Smoky Mountains. All of these occurrences suggest a high trade among the Mississippian culture and the Cahokia Indians. One artifact of interest is the Bird man Tablet, a tablet depicting the head of a man, the wings of a bird, and diagonal lines crisscrossing on the back of the tablet, possibly representing a snake. This would fit with the idea of three worlds. Birds representing the skyworld, the man representing our world, and the snake corresponding to the underworld.