Darius I expanded his kingdom into the Indus Valley and westward to Macedonia. By this time, the Persian Empire covered more than 2 million square miles(5,179,976 sq km) and contained more than 10 million people. Whereas the kings before Darius I had devoted their energy to conquering lands to build the vast Persian Empire, Darius spent his time building a sound system for government.

Darius I secured his rule by gaining the cooperation of local rulers, but he also divided his empire into 20 provinces, or satrapies. Each satrapie was under the rule of a satrap, or local governor, who was appointed by Darius I. The satrap was usually a prince from the Persian royal family or a nobleman of the elite class of Persians.

The satrap was responsible for all government functions within his province. He collected all taxes and tributes to be paid to the king. He would oversee economic development of trade and agriculture. Justice for the people of his province was his responsibility. Satraps were given the freedom to make all decisions necessary for their province, but they still answered directly to the king.Within each province, the individual regions and cities were ruled by local people of the conquered land.

To prevent the abuse of power, Darius I also had Royal Inspectors who oversaw the satraps. These officials were called the “King’s Eyes and Ears” and reported directly to the king. From the many lands and regions, large numbers of soldiers were enlisted for the Persian army. These professional soldiers not only protected the borders of the provinces, but since they answered only to the king, they also kept the satraps from becoming too powerful.

With such a vast empire and so many languages among the different provinces, Darius I knew the only way to rule his subjects was to use one common language. Therefore, Old Persian became the official language for the empire. Instead of the cuneiform writing of Mesopotamia, Darius borrowed the Phoenician alphabet for all his recordkeeping.

Darius I created an army of scribes to keep track of the many tributes collected from all his conquered lands. Provinces paid the tribute with their homeland resources. If the region was agricultural, the king collected one-fifth of the harvest. Other provinces might send sheep, horses, mules, minerals, or precious stones.

Babylon was taxed 500 boys each year to be servants in the royal palace. Taxes were a small price to pay for the benefits of peace and protection provided by the king. One common language and the removal of barriers between provinces unified Persia, while at the same time making its citizens wealthy.

Tributes flowed into the royal Persian treasury and the taxes paid for palaces, roads, and canals Darius I began building a ceremonial city to honor the Persian kings of the Achaemenian empire. Work began in 500 B.C.E at Persepolis in the Pars province and continued with successive kings, who each added their own palaces to the grounds , Persepolis was located in the homeland of the Achaemenids and became its spiritual center.

It was also the site of the royal treasury, and each spring the kings came to celebrate the festival of the New Year. The beautiful capital stood until it was burned in 331 B.C.E. by a 23-year-old Greek warrior by the name of Alexander the Great. Yet the great empire and capital had survived for 150 years after the death of Darius I.

Darius I also rebuilt the old Elamite capital of Susa using materials and labor from distant provinces. He brought cedars from Lebanon and timber from Carmania in southern Persia and Gandhara, now known as Afghanistan. Gold came from Sardis in Lydia and Bactria, 1,000 miles (1,609 km) away beside the Oxus River in the foothills of the Hindu Kush, or present-day Uzbekistan.

Ivory came from Egypt and Ethiopia in Africa and Sind on the threshold of India. Stonecutters from Ionia, goldsmiths from Media, brick masons from Babylon,and wood workers from Egypt combined their skills to make Susa one of the most beautiful cities in the Persian Empire.

Tributes also paid for roads that connected the satrapies to the center of the Persian Empire at Persepolis. With new roads, messengers on horseback traveling 200 miles (322 km) per day could quickly inform the king of any developing problems throughout his far-reaching empire. With these roads protected by the king’s armies, travel was safe for all Persian citizens.


Royalty relied upon their scribes to write and read correspondence for the realm. Records show that the kings themselves often could neither read nor write.


Persians borrowed the concept of coinage for trade and taxes from the Lydians whom they conquered. A standard coin in the Persian empire was the daric, which was about the size of a dime and was made of pure gold. On one side was the image of the king holding a bow, so it got the nickname of an “archer.”


From the Persians, we have the word, “paradise.” Their paradesios–or enclosures–were walled gardens or parks created for the king’s pleasure. Since Persians lived in such an arid country, they created well-watered green spaces filled with trees, shrubs, and flowers. To keep the plants green and sweet, they were planted in neat rows between stone conduits that carried water.


Built by Darius I to connect outlying provinces to the Persian capital of Persepolis, this road connected 111 stations and was 1,600 miles (2,575 km) long.

Cyrus the Great built a series of posting stations to his provinces one day’s ride apart. At the stations were relays of horses and a man in charge who handled messages. If a message was urgent, the relay would go through the night.


The vast expanse of the Persian Empire provided for a large variety of raw minerals, agricultural products, craftsmen’s skills, and knowledge to move freely among its many provinces. The trade routes were well-protected highways, and control of the Mediterranean Sea allowed Persia to trade with more distant lands.

Darius I even built a canal from the Nile River to the Gulf of Suez so that his ships could travel more easily from Egypt to Persia. All the countries in the Persian Empire prospered by the exchange of goods. Whatever was lacking in one province was supplied by another.