Persian Royal Road System

Darius I connected Susa to Sardis with this absolute unit of a road system around 500 BCE. Royal couriers could cover the whole distance in about 7 days using fresh horses at 111 relay stations. Herodotus was so impressed he wrote that famous line about neither snow nor rain stopping them — yes, that's where the US Postal Service motto comes from. This infrastructure is what made decrees like the ones in Ezra and Nehemiah actually enforceable.