It happened in 1980, I think. My father and I were vacationing in Michigan, in the general vicinity of Manistee, when some of the local kids told us about a special place they were calling Mystery Hill, where if you put your car in neutral, it would roll uphill.
It’s a fairly common optical illusion that often results in the creation of a cheesy tourist trap. By happy coincidence, on the day we went out to see it, my father had a toolbox in the back of his truck. It contained a carpenter’s level. We set it down on the allegedly-uphill road and let the universe reveal the truth of the matter.