What from the experience of managing the Persian state is applied throughout the world and today?

Here you can distinguish a single monetary system (coins), as well as the division of the country into separate regions, each of which is controlled by a state person.

So during the reign of Darius 1, the Persian Empire was greatly transformed. A major administrative reform was carried out, which divided the empire into 20 satrapies, in each such area a satrap was appointed. A king alone could not effectively govern such vast territories. Thus, he needed loyal governors in the provinces.