Here is a very well known photo of the surface of Mars with something clearly odd in the image, I cleaned up the original removing the orange/brown caste which Nasa covers every image with. No guesses regarding the obvious artificial structure in view!
Here is the official image, little contrast poor detail !!
Here is the second image which took me around 15 minutes to tidy up using a modest photo rendering package I won't mention the name as this is not an advertising forum. Not only is the main piece in view but all around it are remains of artifial structures, so clear and obvious, enjoy.