Bill Witherspoon’s work ( http://www.sriyantraresearch.com ) and Hans Jenny’s Cymatics experiments (http://www.sriyantraresearch.com/Article/Om/om_sri_yantra_legend.html) inspired us (my wife/muse, her brother and me) back in 2006 to manifest a structure which measures 48 meters in diameter. The top and bottom corners are aligned along the North/South axis.
On each corner and intersection one can see little flowerbed-rings in which we planted small trees (oak, linden, ash and cherry). Around the perimeter we placed 16 cypresses. The (straight) connecting are 20 cm deep furrows that we filled with paramagnetic gravel from the quarry nearby.
The work was done completely by hand using strings, stakes and hoes.
The picture were taken from about 350 meters height.