I was at work (15th floor of a skyscraper) and noticed a beautiful sunset developing when looking out my office window (which faces west). Noticed the object as the sunlight appeared to reflect off of it. At first, I thought the object was a cloud. Then I noticed that it appeared to have substance and a constant shape. It was hovering. I then noticed that there appeared to be a trail leading up to the object. That trail became more and more visible as the sighting continued. I invited several of my coworkers to observe it. We were all somewhat mystified and mesmerized by it. Didnt lose sight of it until I had to leave the building for the day.