Mexico announced Friday that a huge 2,500-year-old Olmec stone sculpture has been returned from the United States. The almost six-foot-tall (two-meter) “Monster of the Earth” sculpture appears to represent the gaping maw of a monster that is big enough to swallow people, and may represent a symbolic entrance to the underworld. Experts say the sculpture is important because of the insights it provides on the cosmological vision of the Olmecs, considered a founding culture of Meso-America.