Multi-Level building

Im currently creating a multi-level bunker for my fps game. I need some advice, make each level of the building (3 in total) in different scenes or in one scene with added floor/ceilings?

Thanks in advance

It depends on gameplay. Do you advance from one floor to the next or can you roam all 3 levels at once.

its explorable, will be part of an fps free roam game.

I’d model them as 3 separate models and parent each level to their own gameobject so you can switch them on/off (especially scripts).
Take a look at occlusion culling as well.

If they’re BIG levels (lots of polygons + textures) you might have to look at streaming chunks of it in as you explore.

Thanks for that occlusion culling looks like the great way to optimise the game.