Wall with light

Hi all…
Watch this wall…
Why i can see it? The room should be completely in the dark!
http://s30.postimg.org/q7p2dtenh/Immagine.jpg

It’s not clear what you’re trying to illustrate

sorry xd
On the left they are several walls… but one is visibile… there is no light on that wall but i can see it… why?