Unidentified box looking object flying across Denver Metropolitan area under intelligent control.I was northbound on Colorado Blvd (aka State Hwy Colorado 2) going to work in Commerce City when I first saw the object about 500 feet high maybe 1/4 of a mile away. I was able to get off the road at 52nd and get out of my car and just watch it. I saw what looked like a big black wall....flying. When reality hit me and I remembered there's nothing aerodynamic about a wall I just stared at the thing all the time looking for a witness, but there was no traffic on an ordinarily busy street. Finally a young Hispanic girl with braces came along but was late to work and I couldn't even get her to look at the object. It continued flying in a southeasterly direction and about 15 minutes later out of sight. Important to note that it flew across Interstate 70 approaching Interstate 270 at right around 2:40PM and anybody looking up should have seen it. The most disturbing thing is I had a good cellphone with a decent camera but I didn't even think about it and i! t remained in it's holster. As I was watching it from behind there was at least one column like looking thing attached to the rear so ultimately I would say it was like a flying box with a propulsion mechanism attached. It also appeared to fly over Interstate 225 a few minutes later and not far from Buckley AFB. No noise heard during the entire encounter and as close as it was, there should have been something.