Answer:
The ancient Greek culture was very varied because there was not a united Greek political entity, instead, ancient Greece was composed of dozens of small city states that were not unified until Alexander the Great.
What was unique about ancient Greek culture is the level of development in many areas. The ancient Greeks made an impact in theatre (Sophocles, Euripides), Philosophy (Aristotle, Plato, Socrates), Math (Pythagoras, Archimedes), and Cosmology (Tales of Miletus, Heraclitus).
These advances were so great that gave birth to western culture. The Romans, who invaded all Greek colonies and eventually conquered them, learned a lot from the Greeks and continued their cultural legacy. After the Roman Empire fell, Europe was still influenced by ancient Greek culture, so much that for almost a thousand years, Aristotle was the most influential philosopher in all of Europe.