This idea probably wasn't unique to the Babylonians, but this approximation of a disc-shaped Earth was fairly commonplace up to and including the Exhilic Period (biblical texts likely being influenced, at least in part, by the Babylonian views though much of the text is certainly constructed of polemic narratives).
https://en.wikipedia.org/wiki/Babylonian_Map_of_the_World
This idea probably wasn't unique to the Babylonians, but this approximation of a disc-shaped Earth was fairly commonplace up to and including the Exhilic Period (biblical texts likely being influenced, at least in part, by the Babylonian views though much of the text is certainly constructed of polemic narratives).