Imperialus
Explorer
Since I was talking about the different entrances I figured I should explain a bit about the entrance that the dwarves in the party would know about. Like the alchemists door the path to the stone wrought stairs can be found off of the main path up the mountain, however the only chance you have of noticing it is if you either know exactly what you are looking for, or have a dwarfs eye for artificial stonework. At the end of the stair (which is a rather precarious climb) there is a sort of 'service entrance' to the top level of the dungeon. Normally only dwarves are able to pass the barrier however, and while the dungeon was sealed at least it was only possible to enter, not to exit, so it may be you will take something of a detour only to find out that half the members of your party are stuck on the side of the mountain.