To answer to your gliterring cave question I beleive there was actually a secret door or a sort, I got my suspicious about 2 things in there.
At the video a bit after when they recovered the axe of helm hammerhand from the box there was a rohirrim guard guarding a narrow passage into somesort of a cave, I could be mistake but that might be 1 way inside the caves who was obstructed when aragorn and the elves fall back to the keep... minute 7.16 or so... my 2nd guess and most right is that there is a secret door on the floor in the main hall thats leads the passage down to the caves as well, thats why aragorn said to barricade the entrance if the uruks found out.
About the main gate
http://4.bp.blogspot.com/_POSCdY4YBZo/T ... deep_1.jpgthis helps a bit although a bit blurry.... but yes the towers are slightly higher than the walls and they are a 3 stair steps on each (that interior weird castle top formation on the tower not sure what was that, but they made that way, that U segment
http://www.freewebs.com/areddawn/helmsdeep1.jpgeven not seeing welll hope their 3D model helms... here you go
http://uppix.net/6/e/5/3eb53952c4432a5a ... 54699c.jpgI hope this helps (the 3D map is not all completed) that is the main structure although they improved it in the end
I expect a good battle from this report.... Although would be more welcome all together as a fight in general.. following step by step the fight was better in my opinion (allow us to focus on reading on the report rather than reading a massive 3000 uruks vs defenders (not saying the 10,000) unless if you have em lol
and in case later on you need a detailed minas tirith map I can toss 2 games pretty much awesome at it :P that 1 already showed and another who allow you to walk through the 1st 3 levels