LARGE Black Diamond shaped craft with three rotating lights on extended arms

I've been in denial for several years about this incident , but for the sake of informing others, I will share my report with all of you. Essentially I saw a black diamond shaped UFO that was the size of a football field (no kidding). I was so close that the detail of it will never leave my memory. I happened to be camping in Banff National park, and I was hiking in a glacier valley when I saw the craft. It had a marble type smooth black surface, with triangular geometric interconnections, which when attached togehter made up the large diamond/triangular shape craft. At the base or bottom of the craft were windows that were lighted up , and positioned in each corner of the triangular craft were three rotating lights (blue/red) which were attached to long extended arms. The craft was silent and seemed to move as such a low speed that it seemed I could probably outrun it. It sailed gracefully in the sky, like it was floating. I've researched to see if others since have seen what I saw and "yes" , others have reported seeing the exact same thing locally and internationally (example Belgian UFO incident 1989). It's really hard to summarize in words what I saw, but believe me when I say, this was not from our known technology existing on Earth.
Date is approximate.  Report is anonymous.  We would like to communicate with the witness to obtain more information.  PD