What part of Amnesia scared you the most?

[Atwa]

Prison, Last part of sewer and the Choir.

The prison for the massive amount of monsters.
The end of the sewers where you have to bait the brute was nerve wrecking.
The Choir because when a monster was on you I never had a clue from what direction he came. Also those creepy torture rooms. The Iron Maiden made me jump so high.