"하늘은 우리의 위에 있습니다."
Translation:The sky is above us.
The marker 은 puts the sentence focus on the sky so that it's more like "As for the sky, it's above us." It sort of answers "What about the sky?". In the sentence "Above us is the sky" (I think: 우리의 위에는 하늘있어요) the focus is on "above us" as though you've been asked "What's above us?"