Which empire used the road network known as the Royal Road to connect its territories?

The Achaemenid Empire used the Royal Road to connect its territories across the ancient Near East.

The road was developed and organized under the Achaemenid Persian rulers, especially Darius I, who reigned from 522 to 486 BC. Its best-known route connected Sardis in western Anatolia with Susa, an imperial capital in present-day Iran, over a distance of roughly 2,700 kilometres.

Royal messengers used relay stations to change horses and travel quickly. Herodotus praised the courier system, emphasizing that weather, darkness, and difficult terrain did not normally stop official communications. The road also supported administration, military movement, trade, and the circulation of information across the empire.

The Royal Road was not one perfectly paved highway in the modern sense. It incorporated older routes and passed through varied landscapes, including Anatolia and Mesopotamia. Later empires continued to use parts of this network, which is why it is sometimes mistakenly associated primarily with Rome rather than Persia.