X, or: An Unknown or Secret Variable

His misgivings ended abruptly, but not without certain forewarnings. First (after a long drought) a remote cloud, as light as a bird, appeared on a hill; then, toward the South, the sky took on the rose color of leopard's gums; then came clouds of smoke which rusted the metal of the nights; afterwards came the panic-stricken flight of wild animals. For what had happened many centuries before was repeating itself. The ruins of the sanctuary of the god of Fire was destroyed by fire. In a dawn without birds, the wizard saw the concentric fire licking the walls. For a moment, he thought of taking refuge in the water, but then he understood that death was coming to crown his old age and absolve him from his labors. He walked toward the sheets of flame. They did not bite his flesh, they caressed him and flooded him without heat or combustion. With relief, with humiliation, with terror, he understood that he also was an illusion, that someone else was dreaming him.

Borges, The Circular Ruins

The original short story in Spanish can be found here and also the translations in English and French.