With Darius I, the scepter passed to a new branch of the royal house. Persepolis probably became the capital of Persia proper during his reign. However, the city’s location in a remote and mountainous region made it an inconvenient residence for the rulers of the empire. The country’s true capitals were Susa, Babylon and Ecbatana. This may be why the Greeks were not acquainted with the city until Alexander the Great took and plundered it.