Olmec colossal heads by Matthew Stirling in 1938 spurred the first archaeological investigations of Olmec culture. Seventeen confirmed examples are known from four sites within the Olmec heartland on the Gulf Coast of Mexico. Most colossal heads were sculpted from spherical boulders but two from San Lorenzo Tenochtitlán were re-carved from massive stone thrones. An additional monument, at Takalik Abaj in Guatemala, is a throne that may have been carved from a colossal head. This is the only known example from outside the Olmec heartland. Dating the monuments remains difficult because of the movement of many from their original contexts prior to archaeological
Chiapa de Corzo, Chiapas important because it shows a Mixe–Zoque–Olmec culture which eventually split from the Olmec. The development of the ancient city has been divided into a number of phases. The earliest and most important are the Escalera or Chiapa III (700-500BCE) and Francesa or Chiapa IV (500BCE to 100CE) phase. Olmec influence is strongest in the Escalera phase when it became a planned town with formal plazas and monumental buildings. However, contacts with Mayan areas is evident as well. However, even during this phase, there are significant differences in architecture and pottery which suggest a distinct Zoque identity from the Mixe–Zoque/Olmec cultural