Soa como o The Wall of Darkness de Arthur C. Clarke :
Many and strange are the universes that drift like bubbles in the foam upon the River of Time. Some – a very few – move against or athwart its current; and fewer still are those that lie forever beyond its reach, knowing nothing of the future or the past. Shervane’s tiny cosmos was not one of these: its strangeness was of a different order. It held one world only – the planet of Shervane’s race – and a single star, the great sun Trilorne that brought it life and light. Shervane knew nothing of night, for Trilorne was always high above the horizon, dipping near it only in the long months of winter.
So he walked on: and when presently an icy hand fastened itself upon his heart, he did not pause as a man of lesser courage would have done. Without flinching, he watched that shockingly familiar landscape rise around him, until he could see the plain from which his journey had started, and the great stairway itself, and at last Brayldon’s anxious, waiting face.
For a moment he had a sudden, inexpressibly poignant vision of another stairway, watched by another Shervane, falling in identical ruins on the far side of the Wall. But that, he realised, was a foolish thought: for none knew better than he that the Wall possessed no other side.