The ancient empire located in what is now modern-day Iran is the Persian Empire. At its peak, during the Achaemenid period (circa 550-330 BCE), it became one of the largest empires in history, extending from the Balkans to the Indus Valley. The Persian Empire is known for its remarkable achievements in administration, architecture, and commerce. It also established a complex system of roads and communications, facilitating trade and cultural exchange. Notable rulers, such as Cyrus the Great and Darius the Great, implemented progressive policies, including respect for local customs and religions, which helped maintain the empire's vast diversity.