Caravanserais were a common feature not only along the Silk Road, but also along the Achaemenid Empire's Royal Road, a 2500 kilometers ancient highway that stretched from Sardis to Susa according to Herodotus: "Now the true account of the road in question is the following: Royal stations exist along its whole length, and excellent caravanserais; and throughout, it traverses an inhabited tract, and is free from danger." "