Here's some scan from the "Worlds of" reference book. It supports the Palpatine death shaft/reactor shaft=Vader's lift shaft idea.
Since Picasa has given me trouble before here, I'm not going to try to embed the images:
http://picasaweb.google.com/lh/photo/GdUxMm8Ycy5g0YI-d0XEyA?feat=directlink
http://picasaweb.google.com/lh/photo/TO5jewSRc3fI9I3b3b4MNw?feat=directlink
The caption to the reactor shaft says "Open shaft surrounding turbolift yawns like an abyss and leads directly to Death Star's power core, 400 km (250 miles) below"
Although I know this is EU, it would be cool to have a hint of this:
http://picasaweb.google.com/lh/photo/xFzSRxtWEKb-lUf_tNoRFg?feat=directlink
Sorry about the scan quality, that book really is too big to fit on a scanner.