Floor 13

Because 13 is considered an unlucky number, some tall building's lack a Floor 13. Sometimes the floor is simply renumbered as 12a and at other times it is missed out altogether.

Conspiracy theorists often suggest that the thirteenth floor in government buildings is not really missing, but actually contains top-secret governmental departments, or more generally that it is proof of something sinister or clandestine going on. This implication is often carried over, implicitly or explicitly, into popular culture. For example in the films The Thirteenth Floor and Being John Malkovich and the computer game Floor 13 by Virgin Interactive.