Under Darius l's ruling, a bureaucracy was developed in which the government was managed under different departments. New systems were introduced, such as roads, mail, methods of payment, and new laws.
Tolerance between the different religions and cultures helped unite the empire. The different religions were Judaism, Christianity, Islam, and a man named Zoroaster was sharing about a god named Ahura Mazda.
As new systems were developing, the economy changed dramatically. A new form of trade was created by exchanging goods for coins. This helped expand trade throughout the empire.