I was in my car on my way home from work traveling southbound on highway 270. I was traveling between 60-65 MPH. It was still rush hour traffic. It was still a clear,bright day at that hour. Between Big Bend and Marshall Road there is a clearing on the right side of the highway that gives a very good view of part of Fenton and Valley Park, as well as a bit of Unger park. As the clearing afforded me this view, I then saw the object. It was metallic grey. It was the shape of a cylinder with a sphere above it. The cylinder was perpendicular to the ground. It was hovering. It appeared to have many different mechanical devices attached to its "hull." The largest of these objects appeared to be support beams that attached the cylinder to the sphere. There were many of these support beams and they appeared to be very sturdy. It was very difficult to get a frame of reference as to its size, relative position to the highway, and how far above the treetops it was. I will say it was a very large object, probably at least, the size of a small 4 to 5 story office skyscraper. It made no noise, but I may have had the windows open and my radio on, which of course may have drowned out any noise the object was making. At first I thought it COULD be a balloon of some sort, but I dismissed that idea because of the metallic nature of the object and the fact that there is no balloon that I know of that would have that many objects attached to its surface. It simply hovered in place the entire time it was in my field of view. I was in shock at first, then I was excited and elated. I had a great need to see it again and even considered diverting my course and attempting to track it down. I lost site of it due to trees and cliffs that blocked the view of any vehicles traveling southbound until you reach the I-44/270 interchange, which is a very large valley. I looked back when I reached this point and the object was gone. It took approximately 30 seconds to reach this next visible viewing area. I am fairly certain it was high enough that had it remained in place I would have at least seen the top of it at that point.