There were many great rich cities along the Silk Road that are now just ruined, with little left of their tales of immense wealth. Merv in Iran, for example, had perhaps 500,000 people there at its peak, was a major centre of learning, and is now just a raised shell in a desert. The point is, people and wealth move, civilisation and empire grows, lives, and dies. It is never fixed, and it definitely never stays the same forever.
The Greatest Theft Never Known