What lesson did ancient Greece teach society?

Answer 1

Although the whole thing is largely a myth invented by the British poet Lord Byron in the 19th century who was drumming up support fot the Greek uprising against the Ottoman Empire, the answer sought usually is that "Greece is the birthplace of democracy".

In reality, Most of ancient Greece never had or even considered democracy, and in Athens - that for some time had a democracy of sorts - the few powerful families of the city saw to it that real power remained firmly in the hands of their family members.