What two tools helped Darius hold together his empire?

Darius I utilized a combination of an efficient administrative system and a network of roads to maintain control over his vast empire. The administrative system included satrapies, or provinces, each governed by a satrap who reported directly to Darius, ensuring local governance while maintaining central authority. Additionally, the Royal Road facilitated rapid communication and trade across the empire, reinforcing connections between distant regions and enabling effective governance. Together, these tools promoted stability and integration within the diverse territories of the Persian Empire.