OOC:
Keep your Inspiration, @rpgventurer
No check really necessary. Success is mostly just a matter of time-thing.
The door is no longer able to serve it's purpose of keeping anyone out. The heavy wood paneling is brittle and mostly hollowed by insects and rot and time. And the metal bindings of the door are corroded and the nails which once held it all together have nothing substantial to hold on to any more.
So although you are all tired, it's really just a matter of knocking things completely loose and prying an opening apart. For the door itself is unopenable - the metal of it's bindings corroded and become one with the metal and stone frame that was installed to make it impenetrable in it's time - but a hole can relatively easily enough be made through the door itself.
On the other side of it, there is a narrow hallway that cuts perhaps 10 meters into the stone before ending in a small circular room with only enough room for maybe 9 men to stand in it (and only then if they were packed shoulder-to-shoulder-to-shoulder). There is also a steep spiraling staircase, only wide enough for 1 man to move up or down at a time, that goes up into darkness.
The steps are covered in a thick layer of dust that demonstrates that no one has walked up or down them in a very, very long time. The air is stale, and the walls have water-marks and accumulating whitish-yellow sediment running in rivulets down the walls from centuries of drainage from the veins of the earth here.
They spiral up for... it's hard to say how long... each stair is nearly a full foot tall, and you figure you must have taken nearly a hundred of them by the time it stops it's upward climb. Which, in fairness, is probably not as far as you figure you had to descend the mountain to find the bottom of the peak-cliff and the hidden door.
So, you estimate you're somewhere in the heart of the mountain peak, but likely still below the stronghold itself. You arrive at a landing that is very similar to the one at the bottom.
The room is barren and appears to have... no normal door or exit. The only indication of anything is a small, square-shaped seam in the stone wihich has a rather uncorroded steel ring mounted in the center of it.
You can hear nothing on the other side.