Studying the ancient routs of Iran and Mesopotamia two main criteria must be considered including trade and political and military movements. The first integrated trade system was founded in these eras.
Owing to the very large the Achaemenid empire, Achaemenid administration needed many roads to be informed of the satraps affairs. It is one of the reasons which the Achaemenid empire recognized a few capitals. At that times overland routes, maritime routs advanced.it was although mainly for political reasons, it led to improvement of trade.
Construction and maintenance of these roads including road facilities such as house of couriers, stone road signs, and deployment of forces for security of roads played the most important role in improving trade and economic situation.
In order to achieve this goal and take its unified form, Persian Empire embarked on constructing roads which the most important one was Royal Road. Houses of couriers were built at certain distances from each other and they provided couriers with fresh horses on the course of the travel from one station to another. These horses were the quickest means of communication at that time.
Many historians such as Herodotus, Xenophon and etc. were surprised by visiting this road and. This road was very important in LASHKAESHI at that time and played an important role in trade and later stretches of the Royal Road across the central plateau of Iran are coincident with the major trade rout known as the Silk Road.
Later was along the Silk Road. The Royal Road was supported by House of Couriers, food storages.
These are the things that Herodotus described as follow: There were Royal stations and beautiful resting places along the way
