I think that anecdote is from the Anabasis by Xenophon and refers to Assyrian city of Nineveh. Babylon was still occupied during the time of Herodotus and was one of the biggest cities in the world at the time. (the book spends some time discussing Cyrus's conquest of Babylon).
I thought it was Xenophon. MSCopilot assured me it was Herodotus. The irony! ;0)
(I spent a few minutes checking, but couldn't find the original quote)
Given the context of the thread, what you have done here fits so perfectly.
The city of London was abandoned for about 400 years and fell into ruins after the people who built it left.