Are you missing a tank tread?
A few weeks ago I saw this tank tread at Sherman and Girard. I figured maybe somebody was using a Bobcat or other small construction machine and the tread fell off, but they'd be back to get it. But weeks later, it's still there.
One would think this is something you'd need, or if you didn't need it, you'd throw it away. If not, it's the weirdest case of littering I've ever seen.