No two are alike: The colossal stone heads of Olmec in Mexico

Name: Olmec colossal heads

What they are: A series of massive heads that were each carved out of a single basalt boulder, often transported from miles away, during the Olmec civilization, an agricultural Mesoamerican culture and the earliest known society in what is now Mexico. Each of these imposing artifacts averages about 10 feet (3 meters) tall and weighs 8 tons (7.3 metric tons). Artisans used stone tools to shape them, adding in details such as pupils in the eyes and dimples in the cheeks, chins and lips, before painting the pieces in bright colors, according to the World History Encyclopedia.

Where they were found: Mexico, specifically in Tres Zapotes in Veracruz, and the Gulf Coast

When they were made: 1200 to 400 B.C.

What they tell us about the past: Of the 17 known Olmec colossal heads found across Mexico, no two look alike. For instance, one is decorated with a crown engraved with jaguar paw prints while another wears a headdress. This has led archaeologists to think that each of the massive statues depicts a specific ruler. 

While it remains a mystery whose likeness the heads portray, one researcher identified a single statue, known as Colossal Head 5, as a second-millennium B.C. ruler from San Lorenzo, the oldest known Olmec city.

Related: Twin 'grumpy mouth' reliefs of Olmec contortionists discovered in Mexico