I was watching a documentary on the Fukushima nuclear disaster in 2011, and the narrator mentioned that a total evacuation of Tokyo was a possibility if things had worsened, saying that it would be "unprecedented in modern history."
That got me wondering about not-so-modern history, so I thought I'd ask here. I'm specifically curious about near-total abandonment, rather than something like the evacuation of children from London during WWII.
Athens, famously, was evacuated onto ships to escape the approaching Persian army during the Greco-Persian wars, just before the battle of Salamis.