Whatever that dish is, it can’t be a secret. Not in these days of Google Earth.
I can easily imagine immortal people creating secret places to hide. It would only make sense for them to do so. Otherwise, they’d have to change identities every fifteen years or so, and, as Glenn points out, that must have become progressively more difficult in recent times. I can even imagine that they live in subterranean tunnels, providing (perhaps) a rational origin for cult theories about underground Illuminati. And, certainly, hiding in a less-traveled area like rural Oklahoma would only make sense. But they wouldn’t signal their secret locations by placing giant domes on top. — Stephen