I saw a large rectangle hanging over north Seattle, WA

My particular sighting was not a craft of any kind but it was very interesting. What I saw was a rectangle in the sky sitting over Seattle Wa. It looked so obvious that I thought there might be something on the news or people talking about it. But there wasn't. I told a few people, but you can image the response someone gets for seeing a rectangle in the sky. This was not a UFO. I only had a very short view of this due to traffic and trees. The shape of this was like a rectangle drawn on a piece of paper. It was just hanging there. I could not say the size of it but there was definitely enough size to it to make it easy to see looking across Lake Washington over to perhaps the north Seattle area.(appox. 4 to 5 miles...maybe less).  I was thinking that it might be a gate to another dimension. I am 58 years old and have never reported a strange sighting before. It was a bright and clear, blue sky, summer afternoon. That rectangle was there and I will never say otherwise.
Witness indicates that the date of the event is approximate.  PD