Darius I built the original Royal Road linking Susa and Sardis.
The road crossed the Achaemenid Empire from the Persian heartland toward western Anatolia. Herodotus praised its stations, guards, and courier system, reporting that royal messages could travel the route far faster than ordinary travelers. The road was therefore both a transport network and an instrument of imperial administration.
Susa was an important royal and administrative center, while Sardis was the former Lydian capital and the western terminus of the principal route described by Herodotus. The road did not consist of one modern paved highway; it connected existing routes, bridges, stations, and guarded crossings.
Darius’s communications system helped the king receive reports and issue orders across great distances. The later phrase “neither snow nor rain nor heat nor gloom of night” comes from Herodotus’s description of Persian couriers, not from an official Persian motto.