From: http://www.area51central.com

Crop circles are a less talked about phenomena which many link to UFOs. They are linked to UFOs because many people believe that it is visitors from outer space who make the circles and patterns in the crops as a form of communication.

However there will always be sceptics. They say that it is just a form of mad graffiti or a way of getting attention for the people who go out at night in the darkness and make near perfect geometrical patterns by laying down the crops. Some of the simple circles could be done quite easily, ladders can be used to get from the edge of the field to the canvas without leaving a trail and then large circular stencils or giant geometry equipment could be used to make the patterns. This would not apply to the huge and amazingly complex patterns however. How is it possible to make such intricate patterns in the dead of night without anyone noticing. Whatever or whoever makes these crop circles are exceptional beings and I would love to watch them doing performing their art so I could know for sure what they are.

The first reported crop circle was in 1678, there have been over 5000 reported cases since.