What's that tower?

That's the tower. It's a gigantic superstructure and no one actually knows what it is. We know it's been here since at least the dawn of humanity because there are cave drawings that we're pretty sure involve it. It seems to be capable of selectively allowing things in it? Like, it even denies access to machines we've made to try to study it from a distance. But only some of them? And we're not quite sure what the criteria is but it seems to be based on their ability to interact with the world? And how does it know anyways? You can nerd out about this thing for hours.

You can't believe you live so close to it without living close to its shadow.

You do feel bad for the people who live close to its shadow, though.