- International Highway of Darius the Great
The Royal Road of the Achaemenids was a major intercontinental thoroughfare built by the Persian Achaemenid dynasty king Darius the Great ( 521 – 485 BCE ) . The road network allowed Darius a way to access and maintain control over his conquered cities throughout the Persian empire . It is also , ironically enough , the same road that Alexander the Great used to conquer the Achaemenid dynasty a century and a half later . The Royal Road led from the Aegean Sea to Iran, a length of some 1,500 miles ( 2,400 kilometers ) . A major branch connected the cities of Susa , Kirkuk , Nineveh , Edessa , Hattusa , and Sardis . The journey from Susa to Sardis was reported to have taken 90 days on foot , and three more to get to the Mediterranean coast at Ephesus . The journey would have been faster on horseback , and carefully placed way stations helped speed the communication network . From Susa the road connected to Persepolis and India and intersected with other road systems leading to the ancient allied and competing kingdoms of Media , Bactria , and Sogdiana . A branch from Fars to Sardis crossed the foothills of the Zagros mountains and east of the Tigris and Euphrates rivers , through Kilikia and Cappadocia before reaching Sardis . Another branch led into Phyrgia .
- Not Just a Road Network
The network might have been called the Royal " Road " but it also included rivers, canals , and trails , as well as ports and anchorages for seaborne travel . One canal built for Darius I connected the Nile to the Red Sea . An idea of the amount of traffic that the roads saw has been gleaned by ethnographer Nancy J. Melville , who examined ethnographic records of Nepali porters . She found that human porters can move loads of 60 – 100 kilograms ( 132 – 220 pounds ) a distance of 10 – 15 kilometers ( 6 – 9 miles ) per day without the benefit of roads . Mules can carry loads of 150 – 180 kg ( 330 – 396 lbs ) up to 24 km ( 14 mi ) per day ; and camels can carry much heavier loads up to 300 kg ( 661 lbs ) , some 30 km ( 18 mi ) per day .
- Pirradazish : Express Postal Service
According to the Greek historian Herodotus , a postal relay system called pirradazish ( " express runner " or " fast runner " ) in Old Iranian and megaregion in Greek , served to connect up the major cities in an ancient form of high - speed communication . Herodotus is known to have been prone to exaggeration , but he was definitely impressed with what he saw and heard. There is nothing mortal that is faster than the system that the Persians have devised for sending messages . Apparently , they have horses and men posted at intervals along the route , the same number in total as the overall length in days of the journey , with a fresh horse and rider for every day of travel . Whatever the conditions — it may be snowing , raining , blazing hot , or dark — they never fail to complete their assigned journey in the fastest possible time . The first man passes his instructions on to the second , the second to the third , and so on. Herodotus , " The Histories " Book 8 , chapter 98 , cited in Colburn and translated by R. Waterfield .
- Way Stations
Even ordinary travelers had to stop on such long journeys . A hundred and eleven way - posting stations were reported to have existed on the main branch between Susa and Sardis , where fresh horses were kept for travelers . They are recognized by their similarities to caravanserais , stops on the Silk Road for camel traders . These are square or rectangular stone buildings with multiple rooms around a broad market area, and an enormous gate allowing parcel - and human - laden camels to pass under it . The Greek philosopher Xenophon called them hippo , " of horses " in Greek , which means they probably also included stables .
A handful of way stations have been tentatively identified archaeologically. One possible way station is a large ( 40 x 30 m , 131 x 98 ft ) five - room stone building near the site of Kuh-e Qale ( or Qaleh Kali ) , on or very close to the Persepolis – Susa road , known to have been a major artery for royal and court traffic . It is somewhat more elaborate than would have been expected for a simple traveler's inn , with fancy columns and porticoes . Expensive luxury items in delicate glass and imported stone have been found at Qaleh Kali , all of which leads scholars to surmise that the site was an exclusive way station for wealthier travelers .