Royal Road

The Persian Royal Road was an ancient highway reorganized and rebuilt by the Persian king Darius the Great (Darius I) of theAchaemenid Empire in the 5th century BC.    Darius built the road to facilitate rapid communication throughout his very large empire from Susa to Sardis ("centralized rule is the victim of time and distance," Robin Lane Fox has observed in this context).  Mounted couriers could travel 1,677 miles (2,699 km) in seven days; the journey from Susa to Sardis took ninety days on foot. The Greek historian Herodotus wrote, "There is nothing in the world that travels faster than these Persian couriers." Herodotus's praise for these messengers—"Neither snow, nor rain, nor heat, nor darkness of night prevents these couriers from completing their designated stages with utmost speed"— was inscribed on the James Farley Post Office in New York and is sometimes thought of as the United States Postal Service creed.

The course of the road has been reconstructed from the writings of Herodotus,  archeological research, and other historical records. It began in Asia Minor (on the Aegean coast of Lydia, about 60 miles east of İzmir in present-day Turkey), traveled east through what is now the middle northern section of Turkey, (crossing the Halys according to Herodotus) and passed through the Cilician Gates to the old Assyrian capital Nineveh (present-day Mosul, Iraq), then turned south to Babylon (near present-day Baghdad, Iraq). From near Babylon, it is believed to have split into two routes, one traveling northeast then east throughEcbatana and on along the Silk Road, the other continuing east through the future Persian capital Susa (in present-day Iran) and then southeast to Persepolis. Of course, such long routes for travellers and tradesmen would often take months on end, and so during the reign of Darius the Great numerous royal outposts (Caravanserai) were built.

Because the road did not follow the shortest nor the easiest route between the important cities of the Persian Empire, archeologists believe the westernmost sections of the road may have originally been built by the Assyrian kings, as the road plunges through the heart of their old empire. More eastern segments of the road, identifiable in present-day northern Iran, were not noted by Herodotus, whose view of Persia was that of an Ionian Greek in the West; stretches of the Royal Road across the central plateau of Iran are coincident with the major trade route known as the Silk Road.

However, Darius I made the Royal Road as it is recognized today. A later improvement by the Romans of a road bed with a hard-packed gravelled surface of 6.25 m width held within a stone curbing was found in a stretch near Gordium  and connecting the parts together in a unified whole stretching some 1500 miles, primarily as a post road, with a hundred and eleven posting stations maintained with a supply of fresh horses, a quick mode of communication using relays of swift mounted messengers, the kingdom's pirradazis.

The construction of the road as improved by Darius was of such quality that the road continued to be used until Roman times. A bridge at Diyarbakır, Turkey, still stands from this period of the road's use. The road also helped Persia increase long-distance trade, which reached its peak during the time of Alexander the Great (Alexander III of Macedon).

In 1961, under a grant from the American Philosophical Society, S. F. Starr traced the stretch of road from Gordium to Sardis, identifying river crossings by ancient bridge abutments. 

Euclid is said to have replied to King Ptolemy's request for an easier way of learning mathematics that "there is no Royal Road to geometry," following Proclus. 

Charles Sanders Peirce, in his How to Make Our Ideas Clear (1878), says, "There is no royal road to logic, and really valuable ideas can only be had at the price of close attention." This essay was claimed by William James as instrumental in the foundation of the philosophical school of pragmatism. Sigmund Freud also famously described dreams as the "royal road to the unconscious"  

The Royal Road to Romance (1925) is the first book by Richard Halliburton, covering his world travels as a young man from Andorra to Angkor.