The Devil, king of evil, is one of the most interesting spiritual concept, for if one can't be sure of God's existence, the existence of evil and of entities who/which impersonate that are beyond doubt.
I always thought that the Edificio Telefónica is the place where the devil lives (New York as suggested in the movie The Devil's Advocate is also a good place but that would be too trivial and trendy, the Devil is subtle).
A sculpture from Jacob Epstein representing The Archangel Lucifer as a mixture of male and female attributes, in Birmingham's round gallery with the other forces of nature. The style of Epstein was particularly apt at depicting the devil (as well as Einstein).