Darius I was largely successful as a ruler. He expanded the Persian Empire to its greatest extent, conquering new lands and forming a vast and powerful empire. He implemented infrastructure improvements, such as the construction of the Royal Road and the establishment of a standardized currency, which helped to facilitate trade and communication throughout the empire. Darius also divided the empire into administrative districts called satrapies, which were governed by appointed officials, allowing for more efficient governance. He was also known for his tolerance of different cultures and religions within the empire, which helped to maintain stability and harmony among his diverse subjects. Overall, Darius I was a successful ruler who left a lasting legacy of expansion, organization, and tolerance within the Persian Empire.