This is the forum for helping you out if you're stuck or if you want to discuss the nitty gritty details of the dungeons within Mount Grimrock. Warning: forum contains spoilers!
For anyone like me that did not find the answer in any other useful forum...
The refered iron gate is NOT the one next to the resting spot. It's actually the GEAR door in the second hall with the statues, where the stairs to go down are.