Circular, 2 storys, rotating mirrored windows

I know this happened a long time ago, but I feel a need to this day to talk about it.
 Me and my cousin were fishing out near the bay.. just a few miles from the Oakland International Airport in California, when we stumbled upon what appeared at first to be a building of some sort.
 but it was no building.  It was 2 storys tall circular in shape about 35 feet wide, it was the shape of a round cake.  It was completely covered in mirrors.. .the bottom half was stationary, wihle the top half rotated quickly in a clockwise position.
 The object made a weird reverberating humming noise, very eerie sounding we rode our bicycles down this trail almost every single day!  But that day changed my whole life.  My cousin got scared, real scared and took of on his bike as fast as he could, he left me out there.  I stared at the object for about a minute before I myself became scared.
 The mirrors on the bottom half were completely mirror, but the top half the mirrors were somewhat translucent and I could see several figures standing in the top half, even though it was rotating quickly I could still see in clearly and see figures standing completely still.
 Maybe if anybody else has seen anyting like this they can talk to me my email address is ((e-address deleted))@hotmail.com
Date may be approximate, although witness does not indicate that fact.  Witness elects to remain anonymous.  PD