Babylon

Babylon was the capital city of Babylonia, a kingdom in ancient Mesopotamia.

Background
When speaking with Joshua Graham, he recites a passage from the Bible that mentions Babylon. Gameplay-wise, there is an achievement called O Daughter of Babylon.

The location is also mentioned as a possible answer to questions in the Pioneer Scouts mammologist and gardener exams.

Appearances
Babylon is mentioned in the Fallout: New Vegas add-on Honest Hearts and in the Fallout 76 update Wild Appalachia.