Let's learn about ancient Persia and Darius and learn things that may relate to the story.

Darius I (522-486 BC), also known as Darius the Great, was known for his good government administration.  The story of Daniel mentions satraps, who ruled large areas of land like regional governors.  (See the map below to see the satrap regions.)  Darius gave his satraps clear borders to govern.  The satraps had to provide Darius both military troops and money from the region they governed.  Darius didn’t want the satraps to get greedy and made sure they couldn’t tax people too much.

Darius I was also a military leader and expanded the Persian empire during his rule.  At the height of its reign, Persia had five capitol cities.  Babylon was one of those capitals.  Babylon revolted against him in 522 BC.  Darius put down the revolt, but not without a struggle.

Darius I is famous in Greek literature for being the king that send troops by sea to fight the Greek army at the Battle of Marathon.

The map below shows the size of the Persian Empire shortly after Darius's reign in 480 BC.

Darius would have had Magi to interpret mystical signs and dreams to him.  The king would have had multiple wives and many children in the palace complex.  He would have had wise advisors, physicians, guards and soldiers, scholars, and artists. 

Internal rivalries were not uncommon in the Persian royal palace.

Persia also had a complex bureaucracy to handle matters of taxation and wages, diplomacy and politics, tradesman and craftsman for palace improvements, military and food supply chains.

Persia had many tribes with many local religions with many gods.  The religion of Zoastrianism was also very prevalent in Persia and Darius would have has some connection with this religion. The religion emphasized a dualistic battle between the powers of good and evil, order and chaos, which would ultimately result in the victory of good. During the time of Darius, these two religious elements of local paganism and Zoastrianism would have combined in some way. We know that Darius considered his main god to be Ahuramazda, the Wise Lord. But he may have worshiped other gods as well.

Perhaps because there were so many local religions in Persia, Persian kings tended to be tolerant of other religions in places they conquered. The book of Nehemiah mentions that it was a Persian king that allowed Nehemiah to return and rebuild the wall of Jerusalem, which led to a religious revival among the Hebrew people.