Hexen Episode 01 map

I quickly made a massive map of Hexen Episode 01 to compliment the official walkthrough at http://www.raven-games.com/hxwalk/e1solve.php

http://members.lycos.co.uk/andrewwan1980/hexen_episode02.gif

There is one thing bugging me. What thing/switch actually activates in "Guardian of Ice (2)" (Gate 6) that enables Gate 5 & 7 to be open?

First off, that's a great map. Reminds me of my old RPG strategy guides, except I never thought I'd see an FPS game laid out like that.

Unfortunately, I don't know exactly what opens the gates. I thought it was switch I because I'm pretty sure I no-clipped from an earlier point in Guardian Of Ice (2) back to the first exit leading to Seven Portals, without passing by those ice shard wall-turrets, and those gates were open.

There should be a way to check in a map/script editor, but failing that, you could try no-clipping section-by-section out of Guardian Of Ice and back to Seven Portals until those gates open.

I don't have a Hexen editor set up so I can't check for myself right now.