[GenXCub]

Here's the easy description. Stand outside the glass door outside the elevator room that's looking down into the Reddish courtyard. Directly ahead of you should be a doorway into a room. Make an immediate left and you should see a ramp going upstairs.

The room where you found the Mandolin of the Magus is on the opposite side of the idol room... you can always go back to that room, down the ramp to the main room, up the ramp on the other side.

If it is not there, then you didn't throw both switches in the haunted building next to the fort. There should have been one switch to activate the pit (where you find the hinged pot) and one switch that didn't seem to do anything.