Thanks to the wonderful work of SpeedyB64, from Nexus Forums, I have a set of narrow 'conduit' passages, which can be used to provide alternate passage between certain areas. They are very narrow and very dark, and can be accessed through conduit panels in some of the passages.
There's a part of a vault I've never seen. (Haven't really played FO 1 or 2)
These are supposed to be maintenance or 'conduit' passages, which basically run wires and pipes between rooms, levels etc. In the original Fallout 3 you could get a peek into them, but that was it. I decided to open them up and make them a part of the vault's exploration.
glad you did