So, 25 centimeter per pixel? I assume 'cm' means centimeter here. Using paint shop, I found most rocks to be in the size range of 20 to 100 pixels. The largest rock would appear to be 27 meters?

Whoa. That is 88 feet long. Using the same method I arrived at 17 feet wide for the rocks. About the same for height.

That comes out to 25,432 cubic feet of rock. for a single rock. Average weight of 166 lbs. per cubic foot of granite, that would make that rock weight, 4,221,712 pounds. Less on Mars, I guess, the mass would still be the same.

Yes, Stonehenge would look out-of-place from the air too. Certainly, these look as if they are created by intelligence and the shadows tell us the height too, if we know the sun angle.