This is a raw NASA image taken by the curiosity rover at Gale Crater on November 8th of 2016.
These blocks are unlike anything else in the image. Differing in shape and color from everything else around them, they seem oddly out of place and unnatural. Upon zooming in we can see that they possess symmetry, clear straight edges, perfectly straight lines and perfect angles. They look like concrete blocks.
The smaller piece looks like a section of two cinder blocks while the larger piece looks like a cinder block retaining wall with a tiled facade. Are these the remnants of a past or present civilization on Mars? On earth nature has created some cube like structures like those found at Giant’s Causeway in Ireland, but they are never isolated pieces. They are usually made of the same material and many are found together. Nothing similar to what we see here in this image.