
Move the scene so that the scene 0,0,0 origin is in a logical place, preferably one that can be surveyed easily.
Create a scene parent node. This will show up at the Maya origin.
Parent all of the scaled and rotated geometry/camera chunks to it.
Modify->Freeze Transformations to reset all of the scene objects translations/rotations to zero.
Display->Hide->All, then Display->Show->Cameras.
Select all the cameras, open the Channel box (Ctrl-A once or twice)
Highlight all translations and rotations, right click, and select Lock Selected. This way, you won’t accidentally move one of the aligned cameras during the modeling process.
Display->Show->All to return the view.
Select the first chunk’s meshes inside their transform, and do Mesh->Combine to make them one piece. Rename this object to match the chunk.
Do the same for the other chunks’ meshes.
Create a polygon object 200 units high, and place it in the scene near a doorway. 200 cm is about 6’5″, so you can see whether your doorways are correctly sized.
If the scene needs to be larger, scale it up from the root parent node.