I could use this building as a Haunted Barracks, and fill it with skeletons and zombies. Like hundreds of skeletons and zombies. And include some treasure in one or two rooms per floor.
And I'm real tempted to plot out a series of "patrol paths" like those that video game guards follow in stealth games.
Now you are giving me a great idea. I was also thinking something like a Grand Palace for the "Royalty". It looks to be designed that way, but now I am also kind of thinking something closer to a Dragon Warrior type royal Palace.
I love the Undead idea. My favorite type of Creature to throw at my players.