Original in Spanish here. This translation was largely done by reader Maria Villa, with slight modifications were made by me dependent on my own interpretation of the text.
Thanks to Maria, here is the information for where you can find the Spanish original in hard copy:
Julio Cortázar, Último round (Tomo II), Siglo XXI, Madrid, 2009 (1969), pp. 222-224.
More about stairs by Julio Cortázar
Somewhere in the bibliography of which I have no desire to call to mind, it was explained that there are stairs for climbing as well of stairs for going down. What was not mentioned then, however, is that there might also be stairs for going backwards.
Users of these practical artifacts will understand without excessive effort that any stair might go backwards if you ascend giving your back to it, but, in any case, what’s at stake here is the result of such an unheard of process. You may do a test with any external stair —once you overcome the initial feeling of unease, or even vertigo, you will discover in each footstep a new field that not only belongs to the one of the previous step, but also corrects, criticizes and broadens it. Consider how just shortly before that, the last time you have climbed up that same stair in the usual manner, all this background world was abolished by the stairway itself and its hypnotic succession of steps; in contrast, climbing backwards would be enough, so that a horizon limited at first by the garden wall now jump to the small field of Peñaloza, encompassing then the Turkish lady’s mill, explode in the poplars of the cemetery, and with a bit of luck, arrive at the actual horizon, the one defined for us by our third-grade teacher. And the sky, the clouds? Count them when you are at the peak, drink the sky that falls upon your face as if through a gigantic funnel. Maybe later, when you turn on your feet and enter the upper floor of the house to your domestic and everyday life, you will learn that there also you should have looked at many things in that way, that also in a mouth, in love, in a novel, you should have walked up backwards. But be careful, it is easy to trip and fall; there are things that would only turn visible to you as you climb up backwards, and others that won’t give in, afraid of that ascension that forces them to undress to such extent; obstinate in their own level and in their mask, they cruelly take revenge of those who walk up backwards to see the world in a different perspective, the little field of Peñaloza or the poplars in the cemetery. Be careful with that chair; be careful with that woman.