“Come out from her!” says a heavenly voice to the saints (Revelation 18). Come out from Babylon, the harlot city, the doomed city.
Commentators hasten to spiritualize: The command doesn’t require a change of place but only a metaphorical exodus, an exodus of the heart. It’s a flight from pagan culture, not from one location to another.
There’s a point to this, of course. You can leave Babylon and take Babylon with you. You can flee Babylon and remain a Babylonian harlot through and through.
A pagan who converts to Christianity and abandons paganism doesn’t necessarily move away from his home city. But he will stop visiting some places in the city and start frequenting others.
Besides: Places aren’t mere spaces, not neutral holding tanks. Places hold memories, and are marked both literally and metaphorically by their past uses. It’s difficult to have a change of heart without a change of place.