Planning and plotting mostly.

With a great sighing breath and her gloveless hand skimming the wall, she ascended. She saw many strange symbols carved into the stones as she went, but they appeared seemingly at random, alone; presenting no other marking. Some of them looked very fresh, others nearly covered by the moss.
As she circled the massive room she came upon the side vantage. From here she could see that the giant tree, whose circumference must have rivaled that of the capitol rotunda at Highseat, clung to, and sprouted from, the wall. It grew right against the massive stonework in all but a few places. And the stairs she now walked wrapped around and entered one such hollow.
Within was cool, lit by the shifting blue cast from the waters below, contrasting sharply the warm golden green behind and beyond. Here the masonry buckled somewhat; the stairs and wall forming a valley where the tree had lifted them subtly over unknown ages.
Fur and vine grew down the tree, from where it touched the wall above, down it's hanging slope to where it met the stairs. Here and there, moistured beaded up and dripped from the vegetation, falling upon the upset walls and stairs and runneling into the groove they formed. The tricklings disappeared down some crack.
At least, it fell upon and ran down the stairs. The wall, turned and tilted as it was, so that it nearly formed a floor, while not dry as such, appeared unaffected by what drippings found it.