I'm starting a new (large) map, and I plan to build my palace in mid-air to better see the lands under my rule. I want to ensure that when I'm relaxing in my glass-bottomed swimming pool drinking a locally brewed artisanal mana potion I don't get attacked by marauding harpies and wyverns. What's the minimum height at which they appear/the maximum at which I can safely reside?
(I'm aware that having NPCs around will reduce the spawn-rate, but those shameless peasants don't get to live in the sky. They're not worthy.)