The Olmec colossal heads are the most recognized symbol of the Olmec civilization. The height and weights of the heads vary, but the largest head is about twice the height of an average human male. They include seventeen heads found in the southern Mexican cities of La Venta, San Lorenzo Tenochtitlan, Tres Zapotes, and Rancho la Cobata. Each head shows a unique facial expression and wears a helmet bearing distinctive decorations. No two are alike. The origins and meaning of the heads are mysterious, and they are the subject of much speculation among scholars and archaeologists.