Summary : Saw black monolith type object

I was outside in my driveway smoking a cigarette, I looked up at the  stars and there was this very large black rectangle silently moving above me.  There  were no lights and it made absolutely no noise.  It  seemed to be very low, 20 to 40 feet above.  
I watched it go south until it was not in my sight.  I am the kind of person who would be the first to call others over to look at some interesting thing, but I never did.  In fact, I forgot about it until recently, which is weird, because normally something that unusual I would recall.