Darius built the largest Empire the world had yet seen, stretching from India to Eastern Europe, and containing c. 45% of the world’s population. He built a bridge of boats across the Danube, crushed 19 separate rebellions in one year and launched the invasion fleet which was defeated at Marathon by 9,000 Athenians. His claim to be an Angel Investor, however, lies in the fact that he built the Persian Royal Road, at that time the largest infrastructure project attempted outside Egypt.