Dr. Who, for those who are unfamiliar, is a very long running British science fiction television program with a fanatical following. The “Castrovalva” serial aired in 1982.
The fifth Doctor, played by Peter Davison, needs a place to recover and is taken to the city of Castrovalva. The city is a maze, a paradox, and a trap. It is a mathematical construction with M. C. Escher-like properties with no means of escape, any direction a person travels in the city just leads them back to the beginning again.