What's so hard about the barracks? Everyplace you see shadows is frankly skippable, and the sligs-in-backgrounds parts just require fast controls and puzzling.
Hmn, most dangerous place...
I'd say the Scrabanian temple. My spine always freezes at the last part where the scrab chases you, so close to death all the way. Ai. *shiver*
And ofcourse once you've made it, you have to jump through the portal, then you miss the triangle button, and yer toast
And creepy? Hmm... I don't know... Oh!
In necrum, that huge face-tree in the background, I never was able to look at that screen when I was... 6 years old. But I grew to love it anyhow. The background music in those levels rocked aswell.