I have just re-read Jorge Luis Borges' 'The Library of Babel', a pdf of which can be found here.
I love this guy. In almost all of his short stories he pulls off this incredible trick of taking an impossible starting point, but then exploring its implications in such detail that you completely forget the fragility of its foundations. His stories a like a perfect sphere in that respect; they only touch the ground at an infinitely small point, but never-the-less form an immaculate whole in themselves. It's like when physicists talk about maths being beautiful; Borges makes that maths literary.