I remember reading (in some rock magazine a few years ago) a story on the background behind the photo on the cover of Black Sabbath's first album.

Since I of course do not remember which magazine it might have been, and probably don't still have it anyway (shocking, I know!), I decided to search the web.
To me, with this album, Black Sabbath changed music forever by defining the genre of Heavy Metal. 
No one sounded like them and like all great bands, the sum of its parts was greater than the whole of the band.

And before playing the album, it all started with this cover.

I found this article which has great photos, the actual location of that iconic house, and interesting information: