It did not require the Great King to emerge from his palace into a stinking mass of humanity for him to flaunt and represent his sway. The detail of a tax payment, safely logged inside an archive; the glinting on a palace door of rare and precious metals, quarried from an incalculably distant mountain range; the portrayal on a frieze of some humble tributary – an Arab, or an Ethiopian, or a Gandharan – his submission forever frozen by the pattern of the design; all these spoke with perfect clarity of the timeless nature of Persian power.