The Olmec colossal heads are stone representations of heads sculpted from large basalt boulders. They range in height from 1.17 to 3.4 metres. The heads date from at least 900 BCE and are a distinctive feature of the Olmec civilization of ancient Mesoamerica. All portray individuals with characteristics corresponding to phenotypes that are still common among the inhabitants of Tabasco and Veracruz. The backs of the monuments are often flat.