Every Halloween, groups of teens gravitate to the base of a small incline at the cemetery known as gravity hill to conduct similar experiments, or head out to a little incline on East Loma Alta Drive in Altadena, where the immutable force of gravity seems to warp and where people’s perception of what’s up and what’s down gets confused.

And the two mysterious spots are not so unique.

According to the Web site paranormal.about.com, there are dozens such places scattered throughout the United States. More here.