things to see things to touch in chapter 10

okay the sentence summary is Jonas went to the building went in side the door was locked he wandered why it was locked. then he met the old man and the old man asked him if Jonas knew what snow was or if he knew what a sled was and if he ever saw a down hill or heard of one.  My reaction to that is wow how does Jonas not know what a sled is or snow they should at least know what it is in books.  My question is why don't they know what downhill or is there any mountains there cause to me there isn't any.