A building 50 metres away may be some distance to see or to hear, but do not confuse real world distance with the distance you feel it is in your consciousness.
Your consciousness isn't "real" in the same way that building is. It exists purely for you and you alone, and is generated in your head. As such, that building for you is just as far as the chair you are currently sitting on. So - do not stress yourself trying to focus on that building because it is far away, it isn't, neurologically it is only a few millimetres away like every other item in your conscious reality. Don't stress your brain because you believe it's far away and so needs more brain energy!
Maybe the only thing you might need to stress is your eyes if you're trying to look right at it, but definitely nothing else. Think about something far away as if it's right next to you, because that imagery and those thoughts really are right next to you.