Communicating map boundaries

So I’m fairly new to forge and am working on a map set in a sort of hollowed out high rise (kinda like the style in deus ex mankind divided), and I have no clue how to stop people jumping down to the ground floor because they think that it’s a part of the map, when it isn’t.
If there is anyone out there that knows something about this, I would appreciate any suggestions you might have.

Kill Volumes, or add a railing or something to add an aesthetic “hint” that it’s the edge of the map.

Not sure how to stop people from doing this but maybe put kill volumes down there so they know not to do it again.

Invisible barriers are also an option, but they always annoy the heck out of me when people use them. Kill volume is probably the better solution, as others have said.