Oregon Vortex

The Oregon Vortex is a spherical field of force, half above the ground and half below the ground. The word “vortex” simply means a whirpool of force, like a whirling mass of water, especially one in which a force of suction operates, such as a whirlpool or a whirling mass of air, especially one in the form of a visible column or spiral, such as a tornado.
It opened to the public in 1930.

http://www.youtube.com/watch?v=qxkuwWYORJg