Mystery Spots and Gravity Hills

Cars and balls seem to roll uphill, people appear able to stand at impossible angles - all in contradiction to the laws of gravity and physics. What's really happening at these curious locations?

There are dozens of mystery spots to be found around the U.S., and many more gravity hills - places where gravity itself seems to be warped. Our perceptions of up, down, straight and crooked are confused by what some say are powerful gravitational anomalies and dizzying magnetic vortexes. Is that the case, or are our senses being fooled by clever man-made and natural optical illusions?
[link to paranormal.about.com]