Sheffield University Dig.
The immense holes dug for the wooden uprights in the outer circles, shown by the green marker in the background. Aprox 1M deep by 1.5M wide. The shallower hole in the middle is believed to be for a large stone which was missed by the original Cunnington excavation. the shallower scrape to the L centre has been provisionally dated to the Mesolithic period.
(Info from guides)
Jim.
Image credit: Jimit Sept 06
