The Church of Scientology, for which I have zero respect, has a "secret" landing strip and vault in the New Mexico desert.
Boing Boing just had a post about it, with links to aerial photos.
The vault apparently contains the writing of Hubbard and is there as a meeting place for the souls of the faithful after they die. In order to make it easier for the spirits to find, a rather large symbol of scientology is carved into the side of the mountain.