After reading Freud's essay I can really begin to get a grasp of the uncanny from his well written explanations and examples. Freud opens up the essay with a general definition of what uncanny entails,
"There is no doubt that this belongs to the realm of the frightening, of what evokes fear and dread. It is equally beyond doubt that the word is not always used in a clearly definable sense, and so it commonly merges with what arouses fear in general."
This however isn't a general gruesome fear, it's more of an intellectual uncertainty spawning from our own life experiences.
"I can say in advance that both these courses lead to the same conclusion - that the uncanny is that species of the frightening that goes back to what was once well known and had long been familiar."
This is saying that fears for example from our childhood can act as the root of the uncanny. So fears such as fear of the dark, small spaces, being followed, etc. can initiate the feeling of uncanny and also things which we do not want to encounter as Schelling states,
'Uncanny is what one calls everything that was meant to remain secret and hidden and has come into the open'
We also have deep fear for the unhealthy because it brings up fear of malfunction of our bodies,
"To these he adds the uncanny effect produced by epileptic fits and the manifestations of insanity, because these arouse in the onlooker vague notions of automatic - mechanical - processes that may lie hidden behind the familiar image of a living person."
This is why scenes of mental hospitals and also abandoned ones give off the feel of uncanny because it is where or was where people were not acting as they should, instead seemingly being controlled. (Thank you Alan for the tip on Hellingly Hall, the place does have a strange atmosphere to it.)