 The discovery of a colossal head at Tres Zapotes in the nineteenth century spurred the first archaeological investigations of Olmec culture by Matthew Stirling in 1938 . 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 . 
 The discovery of a colossal head at Tres Zapotes in the nineteenth century spurred the first archaeological investigations of Olmec culture by Matthew Stirling in 1938 . Seventeen confirmed examples are known from four sites within the Olmec heartland on the Gulf Coast of Mexico . Most colossal heads <a href='uninflect' title='1'><mark>were</mark></a> sculpted from spherical boulders but two from San Lorenzo Tenochtitlán <a href='uninflect' title='2'><mark>were</mark></a> re @-@ carved from massive stone thrones . An additional monument , at Takalik Abaj in Guatemala , <a href='drop_aux' title='3'><mark>is</mark></a>a throne <a href='null_relcl' title='4'><mark>that</mark></a>may <a href='been_done' title='5'><mark>have</mark></a> been carved from a colossal head . This <a href='drop_aux' title='6'><mark>is</mark></a>the only known example from outside the Olmec heartland . 
The discovery of a colossal head at Tres Zapotes in da nineteenth century spurred the first archaeological investigations of Olmec culture by Matthew Stirling in 1938 . Seventeen confirmed examples r known from four sites within tdaOlmec heartland on thdaulf Coast of Mexico . Most colossal heads was sculpted from spherical boulders but two from San Lorenzo Tenochtitlán was re @-@ carved from massive stone thrones . An additional monument , at Takalik Abaj in Guatemala , a throne may done been carved from a colossal head . This thedaly known example from outside the Olmec heartland .