The Penrose stairway is an impossible figure in which a stairway in the shape of a square appears to circulate indefinitely while
still possessing normal steps (Penrose and Penrose 1958). The Dutch artist M. C. Escher
included a Penrose stairway in his mind-bending illustration "Ascending and
Descending" (Bool et al. 1982, p. 321; Forty 2003, Plate 68). Distorted
variations of the stairway are also depicted in Escher's "House of Stairs"
(Bool et al. 1982, p. 301; Forty 2003, Plate 40).
In the 1998 film The Avengers, Uma Thurman is shown walking down a Penrose stairway and ending
up back where she began.
