Assume you are an evil genius and have a huge (10's of Km wide) floating island fortress, previously concealed by phlebotinium. Of course your evil-genius-floating-fortress have several WMM (weapons of mass mayhem)
- You are in almost all the most wanted lists on the world. After all, your evil genius pride demands it.
- You stamped/engraved your face/logo everywhere on the fortress walls. Such megalomania.
- You are running out of phlebotinium soon, and there is no way to replace it.
- XXI century Earth does not know your fortress exists, but soon will. But they know you as an evil genius, and did I mention you have your face/logo on big banners everywhere?
- You only have concealment to travel 3/4 the equator circunference (thus you can reach anywhere).
- If you pop near the borders or inside the territory of a major government, they will immediately dispatch a strike force.
- You are flying 1800m - 2000m high to avoid altitude sickness.
So the best plan is to get to a safe spot on Earth, get ready to defend yourself and do evil genius stuff.
Where on Earth it would be least threatening to the major powers of the XX century for such a fortress to reappear?
EDIT: I painted the evil genius gag too strong.
Where on Earth it would take the longest for the major powers of the XXI century to mount an offensive on your island fortress?
Lets suppose it happens by early 2016, and no major incidents happen from now to there.