Mind-altering substances were all the rage 1,500 years ago, at least among certain elite members of a South American society.
One of the cities featured an extraordinary facade with an entrance representing the open jaws of an earth monster.
No other site has so far been located in this area, which extends over some 1800 square miles in the Mexican jungle.
Failed monsoons in 14th and 15th century coincide with the Khmer Empire's collapse in SE Asia.
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