Persian Empire was a great empire spreading over the Near East and Asia. They had many accomplishments.
One of the main things they have managed was to build an amazing road system, the first one that connected Asia, Africa, and Europe. The Royal Road was an ancient highway that connected the two parts of the empire, helping the communication and access to the distant parts.
During Darius the Great, the monetary system was unionized in one empire for the first time. The main system was Achaemenid coinage, and its values, Darics and Sigloi.
The Persian Empire also showed kindness toward conquered people, allowing them religious and cultural identifications. People could keep their local traditions. This was their strategic diplomacy, as the practice helped them maintain order and gain trust from the people.