It took me some time to see the areas you marked in the original photo. One of the reasons was that I did not knew if you had used the map-projected
or the non map-projected version.
As you call "Southern shoreline" to a feature that is to the North, I suppose you used the non map-projected image.
In that image the Sun light is coming from the bottom right corner of the image (50.62° clockwise from a line drawn from the centre to the right edge
of the image to the direction of the sun at the time the image was acquired), and that may help distinguish a mesa from a ravine.
Your first image, for example shows a mesa, the "fallen castle" being on one of the mesa's sides.
I downloaded the original, non map-projected IMG file, opened it in The Gimp
(version 2.2.16 has a plug-in to open those IMG
files), applied the "Destripe" filter and changed the levels. After that I resized to 300%.
This is the result.
To me, the "fallen castle" looks just like common vertical ridges on a slope (I hope you understand what I want to say, sometimes I can not find the
Here it is, rotated and resized to 200% from the previous image.
The "terrace" looks like anything, really, I don't see anything out of ordinary here.
The "archway" looks like the shadow of the higher rocks.
The "sand castle" does not look that strange in a picture with more shades of grey.
The "shoreline" does not look that strange if you are accustomed to higher definition images from Mars.
In this image I don't know what it is that you call "the entrance". Is it that dark area? That is the shadow of the side of that small crater.
In the last image I don't see anything unusual.
I would like to ask one thing: why do almost all your images have such a low colour count? There is one (the one with the "sand castle", that has
only 14 shades of grey! How do you suppose to see anything in an image like that, that has lost most of its data?