41 There is some debate as to whether the so-called "Great Circle" was ever a complete circle at all. There are 12 surviving standing stones around the mound of Newgrange out of a possible original 35 to 38 orthostats.

42 One "pit" was found to the east of stone GC-2, which may have been a socket for one of the GC stones in former times. However, during later excavations a series of 70 pits were found in a giant arc to the east of the cairn, so it is not known if a standing stone ever stood at this location.

The Great Circle shown in a watercolour painting in 1775

43 The Great Circle (GC) has an average diameter of 103.6m (340 ft), which is larger than the diameter of Stonehenge, the outer bank of which is 97.5m (320 ft).

44 The stones of the GC consist of greywacke, which is a type of sandstone, as well as limestone, granite and other igneous rocks and stand at a height of approximately 2 metres each.

45 Curiously, a number of the existing GC stones are diametrically opposite each other and many of the opposite pairs are spaced apart by 103.6 (340 feet) which is exactly 125 megalithic yards according to Alexander Thom.

46 Archaeoastronomer Frank Prendergast has produced data which shows that the "Great Circle" stones were astronomical and calendrical in function.

47 Excavations revealed that the Great Circle was erected some time after 2000BC, meaning it was the final stage of construction at Newgrange.

One of the GC stones

48 It is known that the Great Circle was erected when Newgrange was still in use. It had been put in place before the collapse of the cairn, which is obvious from the way the cairn slip material mounted up against the GC stones.

49 When Newgrange was being excavated, one of the GC stones, GC-10, was found lying prone, and was later re-erected in 1973 when archaeologists located its original socket.

50 An implement described by Professor Michael J. O'Kelly as an "iron wedge" was found under the turf near a pit which may have originally been a socket for stone GC-3. The archaeologists speculated this implement could have been used to split the stone - fragments of which may have been found nearby.