Why is the Persian empire so big?

The Persian Empire became extensive due to its strategic location, which facilitated trade and cultural exchange across regions. Its effective administration, including the use of satrapies (provinces) and a standardized system of taxation, allowed for efficient governance over diverse populations. Additionally, strong military capabilities and a policy of tolerance towards different cultures and religions helped integrate conquered lands and maintain stability. These factors combined enabled the empire to expand rapidly and sustain its vast territories.