The level has 4 exit-cubes that return you to the normal level you came from:
- behind the first door from starting point
- at the very far end of the level
- at the top of the reactor room
- and in the room opposite of the reactor room
The last one is a cube in the ceiling of the room. And above it there is yet another exit-cube.
(you can see it when using the Full-Map-Cheat)
Since the cube in question lies beyond the exit-cube one could never ever enter it

I opened the level in \"Descent Level Editor XP\" but - to be honest - I couldn´t find what the surplus cube does.
For reference: it is Cube No. 20 (beyond Cube No. 21)
Does anyone know what this cube is / does / means?
Is there a way to reach it? (Guided Missiles don´t seem to work)
Is this a super-ultra-secret?
Or just an artefact from an earlier design-stage?
Thanks in advance!