A relative of mine recently retired from a teaching post up in the Adirondacks, but before she proceeded to "head for the hills," if you will, she taught her last fourth-grade class a lesson on how roads and streets get built. When she was done, one of her pupils seemed especially entranced, and only had one question: "But how do they make the hills?" Kids say the darndest things, it's true, but adults also make their own hills sometimes, and even have some rather funny sayings about it. Amounting to slightly more than a hill of beans, I suppose, but not enough to make a mountain out of a molehill or anything, the hills were alive with our typo of the day, which turned up 11 times in OhioLINK, and 257 times in WorldCat.
(Herstedhoeje, a artificially created hill 15 km west of Copenhagen, 18 June 2008, from Wikimedia Commons.)