It is difficult to reveal that the picture is fake for ordinary people*, but for the expert eye it will be easy to find out, but how did you manage to identify the original image?
9 out of 10 times such sites reuse pictures that are flipped. So a flipped image searched through google would land you on similar pictures and it is easy to track from there.
Also, even an untrained eye can look at the picture and see how uncanny it looks - that is the uncanny effect of 3D renders. Very rarely can we achieve a realism that does not have that uncanny look.
I've been a 3D renderer for a long time and the most accurate rendition of archviz is traditionally done through VRay and these days through Corona and Arnold.
In this one's case, it was clear that this was a 3D rendered scene and that too doctored. Not that hard to spot.