I didn't know that they could walk to the warp core on ENTERPRISE 1701 I always saw Commander Scott in those little tubes when he was ixing things. Sometimes you can see the ships engine in the background so it was sorta of confusing in my mind where exactly these people were when they were talking. (Delgado and Kirk and Scott.) So i made up a little room in my head.
I based my depiction of the engineering hull layout partly on what we saw of the engineering spaces in the animated series and partly on this schematic by Doug Drexler
, a version of which appeared onscreen in ENT: "In a Mirror, Darkly Part 2." There are more specifics in the acknowledgments at the end of the book.