What are Penrose stairs?
A A haunted stairwell
B A type of plant
C An optical illusion
The ‘impossible object’ was independently devised and discovered by Oscar Reutersvärd and Lionel Penrose. It was Penrose and his son that popularized the design of a staircase that defies physics. The sculpture in our photo is considered a type of Penrose stair.
The correct answer is An optical illusion.