With separated diagrams, the lower E-Level 5 would look rather boring and empty.
Essentially, it's a circular platform surrounding the m-am reaction chamber. The two circular floor openings at 9 and 3 o'clock are ladders that lead down to Engineering Deck 12 (which now needs to be cleared of the "energizers" illustrated in the latest draft a few posts earlier).
The "Kelby" Jefferies Corridor extends to the bow, the "Archer" Jefferies Corridor (same length) to the stern (in the illustration the 3 o'clock energizer corridor on E-Level 4 above "covers" this corridor below / "shields" it from our view).
On that E-Level 5 platform we have at least three ladders (conventional "Environmental Engineering" and/or EMM style) that connect to E-Level 4 above, one at 12 and one at 6 o'clock and one on the port side of the "Archer" corridor.
Once I got to the point of presenting a cutaway this should be much clearer and graphic.