The picture below is from the backyard of someone living in Rhode Island. It shows a large gravel circle with an inner stone circle.
The inner stone circle marks the approximate periphery of a vortex. It is an energy vortex, or what I call a natural vortex that forms in response to human intention. It is pulling in Cosmic Prana (energy) that we attract during meditation, praying or performing a ceremony. Meditating in the vortex would increase your draw of Cosmic Prana.
The two black lines mark two Spirit Lines, or Ley Lines that intersect in the center of the circle. There are several other Spirit Lines that intersect on the property as well.
Given that the vortex is located over the intersection of two Spirit Lines I assume that someone prayed, or did ceremony at that specific location.
Some of you may be able to feel the power of the vortex if you look at the picture.