Olmecs (1200-400 BC) were the first civilization in Central America. They built several cities with stone buildings and temples, as well as the colossal "heads" (up to 9 ft -12ft or 3 m tall) that are their notable legacy. Their civilization was centered on three rivers that empty into the Bay of Campeche in the Gulf of Mexico, along the central east coast of Mexico. They established trade with other native groups in Central America, developed agriculture, and created intricate artwork in pottery, stone, and jade. They may have developed a written system of pictographs even earlier than the Mayan civilization that followed them. The ritual ball game played by later tribes in the region may have started with the Olmecs.