This is the flag of the Athenian Empire. It comes from a world where Athens won the Peloponnesian War. Following the defeat of Sparta, the Delian League was expanded to include the Greek colonies in Italy, the city-states in Anatolia and all of Greece. All of this new territory meant more treasure for Athens' coffers. Athens used much of this new-found wealth to expand its military and navy. The unification of the Greek city-states meant that the Macedonian Conquest never occurred, and Alexander the Great never came to power. Though it was still known as the Delian League, in reality, all of the city-states knew that they were now part of the Athenian Empire.
The threat of Persia was an ever-looming concern. Athens funded many rebellions against Persia in regions such as Egypt and the Levant. Eventually, Athens declared war on the Persian Empire and conquered it in short order. However, most of the territory was lost within a few generations. Athens also went on to conquer Carthage, the fledgling Roman Republic and expanded its territory into Gaul. Athens also expanded into Hispania and the British Isles, but never for too long.
Following this series of conquest Athens began to focus more intellectualism and the acquisition of knowledge. Many libraries and centers of learning were founded across the Athenian Empire. The Athenian Empire never truly fell, but over the years it did lose territory; at its smallest, it was comprised of Greece and Anatolia. However, Greek influence on language, art and culture is felt throughout its former empire and the world at large. In many ways, the Athenian Empire can be seen as the Western world's equivalent of China in terms of influence and culture.
The flag features an owl clutching an olive branch, symbols of Athens patron goddess Athena. The colors of the flag are black and orange in reference to Ancient Greek pottery. The black on the first flag is also a reference to the black sails of Theseus, mythical king of Athens.