Also known as the “impossible staircase”, the Penrose Stairs are an illusion first create by Oscar Reutersvärd in 1937 and later independently made and popularized by an article by Roger and Lionel Penrose in 1959. Based on their previous paper published in 1958 that described impossible triangles, the new article put forth related impossible geometries including the “continuous staircase”. The article would inspire M.C. Escher to create Ascending and Descending in 1960.

The Penrose stairs depict a cyclic staircase, where a person walking up or down them would loop back to where they started.

https://en.wikipedia.org/wiki/Penrose_stairs