What do You See?
Have you seen the pictures of the "Face on Mars" or the "Spire on the Moon"? Are these pictures evidence for extraterrestrial aliens, ancient civilisations or simply for a natural process of the complex structure called the human brain?
Pareidolia is the term used to describe the process of the brain assigning meaning to what it observes when there isn't enough information to get it right. The brain will naturally try to make sense of what it is seeing, and most of the time the interpretation is fairly accurate. But if there isn't enough information, the brain will try to fill in the blanks.
The Moon Spike
Take a look at the picture of moon surface showing an "object" that could be seen in two different ways.
One interpretation is that the dark streak indicated by the arrow is a spire, or spike and the long lighter shaded line is a shadow cast by this spike. The credulous person will immediately jump to this conclusion, and nothing you can say will change what they perceive.
The object does indeed appear to be a spike at first glance. So what is it if it isn't a spike standing up on the moon's surface? Take another look, and this time look at the light line as being the front edge of a sharply rising rocky mound and the lighter area to the right of it being a raised curved mound casting a shadow against the sharply rising edge. Behind the high mound, there is a steep cliff (lower part of the mound on the picture) which is casting the dark shadow behind it and curved down into the crater below.
Seeing a spike at first glance is entirely normal, and is known as pareidolia. Seeing a spike and immediately determining that it must be an alien structure is naive. Continuing to see an alien structure or accepting somebody else's explanation that it is a manufactured spike is credulous. A rational response is to look for what else this could be and will likely result in a more credible explanation. Once you make this connection it is all you can see, and the "spike" no longer jumps out at you.
The Face on Mars
As another example of this phenomenon take a look at the picture on the right of the "Face on Mars" that became so well known in the 1980's. It does look like a face doesn't it?
Now take a look at a later image of "the face" taken by Mars Express from multiple angles and rendered into a 3D image. It no longer looks so much like a face does it?
Whenever you see something that looks a bit unusual the first thing you should think is "what am I really seeing?" not "wow look at what aliens built."