The birds
Aristophanes composed the Birds in 414 BC, little after the Peloponnesian War and the defeat of Athens.
The two heroes are leaving Athens deeply disappointed of the corruption of their society. On their way they meet the Birds and they convinced them to build a new city and a healthy society between the sky and the earth, into the clouds. Still they are worried about the potential success of their attempt, because their compatriots were so corrupted, vicious and calumniators, that they would “pollute” even this imaginary cloud – city.