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The oldest known canals were irrigation canals , built in Mesopotamia circa 4000 BC , in what is now Iraq and Iran .
 Mesopotamia, Iraq, Iran
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Mesopotamia, Iraq, Iran