Tower of Charm
From Glen Cook Wiki
The Tower of Charm is the fortress of the Lady, the capital of the Northern Empire built after her resurrection with the aid of the Ten Who Were Taken. It is an imposing structure and perhaps the best-defended citadel in the world.
It is a gigantic cube of black basalt stone, five hundred feet tall (the equivalent of a forty story building). The stones have been fused with sorcery and are nearly impervious to conventional and magical assault. It is surrounded by a field of broken and left-over basalt, a jumbled field of giant rocks a mile in diameter, "more effective than any moat". The only approach is a clear wedge-shaped path facing north.
The Tower is actually two structures. The outer ring is where the functionaries of the Empire live and work. There is also an interior tower, taking up a third of the volume, which is the Lady's private tower; it has only one entrance and no windows.
The imperial staff at the Tower wears very bright-colored uniforms, which Croaker likens to a peacock; supposedly the Lady designed these herself. What staff we see at Charm is quintessentially professional and competent.
Charm is the site of the largest battle in history, when the massed armies of the Circle of Eighteen attempt and fail to take the citadel; a quarter million men die in that battle, including some of the Taken. Later, Charm easily repels the assault of the crazed Limper, where nearly all other cities and fortresses fall before him.
