The Hanging Keep is less of a keep and more of a complex maze of hallways and pillars. Whatever it once was or was used for has been lost to the ravages of time. It is multi-level and in terrible shape, with large holes in the floors and ceilings. Anything of value has long been scavanged from the crumbling walls.
What makes the keep unique is that it has been spelled to hang in the air, 30 feet up. The spread of the branches and vines nearby have nearly overgrown the structure. The Keep has no known method of access other than climbing up to it using the surrounding flora, which have grown taller than the the Keep itself.
Creatures have been known to inhabit the Keep, using it for shelter from bad weather, but this is only marginal protection given the terrible shape it is in.