The Schroeder stairs, also called Schouten's staircase (Bool et al. 1982, p. 147), are an ambiguous figure that depicts two different staircases at the
same time: one going up from right to left, the other turned upside down. The Schroeder
stairs appear in M. C. Escher's works "Relativity" (Bool et
al. 1982, p. 306; Forty 2003, Plate 53) and "Convex and Concave"
(Bool et al. 1982, p. 308; Forty 2003, Plate 56).
