On Sol 2444...
The Rear HazCam of Opportunity Rover...
Imaged something extraordinary...
![](http://marsrover.nasa.gov/gallery/all/1/r/2444/1R345151840EFFAZIEP1301L0M1.JPG)
The one on the left looks like a ramada, the one in teh center looks like billboards, and the one on the right looks like a building...
It's not part of the rover, as it doesn't come in from the top, it is clearly it's own thing.
I have no idea what they are...