Odd shaped aircraft seen over Peoria ILI saw this craft in the air over downtown Peoria, IL, moving from southwest to northeast in a straight line. It must have been a half-mile in altitude and never changed direction. It was moving very slowly, as if simply being blown by the wind and it made me think it was a balloon for a long time, albeit a very large and strangely shaped balloon. It was shaped like a parenthesis (with the arched part up and was dark gray. I would estimate its length at 30 feet and its height 5. I was really amazed that I could see it for so long and I even saw it through binoculars but am still uncertain as to what it was if not a UFO. Like I said earlier, an odd-shaped balloon is the only thing that comes to mind, as it seemed to be floating with the wind. It never changed its position however, as a balloon might, as it stayed steady in the air except for occasionally rocking slightly to one side. It eventually drifted over the river and out of sight.