THe Archaeological excavations
The first archaeological examination of the Standing Stones o’ Stenness took place in the early 1970s.
Following the destruction of the central "dolmen" in 1972, a seven-week excavation took place over 1973 and 1974. This saw a series of trenches dug around the monument - primarily to prove, or disprove, the dolmen's historical existence.
Led by archaeologist Graham Ritchie, the excavations were enlightening to say the least*.
They confirmed, for the first time, that the remaining stones had once been part of a ring containing at least eleven stones. Although a twelfth socket hole was located (No 12), it appeared to have been unused.
Geological examinations of the surviving stones revealed that five different types of stone were use - a discovery that ties in with Dr Colin Richard’s theory that the stones for the monument, just like Brodgar, were brought to the site from various different, perhaps significant, locations.
The excavators confirmed that the stone ring had been entirely surrounded by a ditch, apart from a single entrance causeway to the north. This stone-cut ditch surrounded an area 44 metres (144 ft) in diameter and was two metres (6.5 ft) deep.
During the excavation, the bottom of the ditch was found to be beneath the water table and therefore kept filling with water. This, together with archaeological evidence of aquatic plants, indicates that while the monument was "in use" the ditch contained water and, therefore, that water was a deliberate element of the design.
Inside the ditch were pottery sherds and the remains of cattle, sheep and dogs (or due to the size, perhaps wolves). These could either indicate that offerings were thrown into it, or that the ditch was used to dump the refuse left over from the ceremonies inside the ring. Bizarrely, two cremated bones from a human hand were also found in the ditch near the entrance causeway.
The central fittings
At the centre of the ring was a large hearth, typical of those found within Neolithic dwellings, such as Barnhouse and Skara Brae.
Constructed from four large stone slabs, laid out flat to form a rectangle, the hearth contained traces of cremated bone, charcoal and broken pottery - finds that strengthened the idea that the monument was once a site of feasting.
Later excavations at the nearby Barnhouse settlement, in the late 1980s, prompted Dr Colin Richards to suggest that an earlier Standing Stones hearth had originally been on the outskirts of the village, and relocated to the centre of the ring**.
The Stenness excavation showed that an upright post had stood in the centre of the ring prior to the relocation of the hearth.
Moving to the north of the hearth and running parallel to the entrance causeway, excavators found the sockets for a pair of standing stones. “Connected” to the hearth by a rough stone path, at some point the stones that stood in this position had been removed and the socket holes filled in.
Slightly to the north of these twin megaliths was evidence of a small, two-metre, wooden structure. Circular depressions at each corner indicated the position of probable corner posts. Tiny deposits of decomposed wood radio-carbon dated giving a date of around 2150BC.
The eastern and western sides of this feature were in line with the double megaliths, prompting the suggestion that the stone formed a “porch or monumental entrance” to the timber structure – these stones may have been removed when the timber feature was dismantled.
In the place where the controversial altar had been raised, there was evidence that some form of stone structure had one stood on the site.
Although the stones that would be used to create the dolmen may have formed a stone setting parallel to the wooden structure and the paired megaliths directly to the south, the stone sockets original stone-holes were destroyed during the 1907 reconstruction.
However, the excavators concluded that two eastern stone uprights were probably in their original position, with the socket hole for the third under the current “tabletop slab”. In this case, the stones continue the northward progression of features leading from the hearth – a pair or standing stones, a stone feature and finishing with a parallel feature constructed with stones.
But because the exact nature of the “dolmen” structure was not clear, it was agreed that the two upright stones of the altar be re-erected and the "tabletop" slab left lying beside them. There they remain to this day.
South of the hearth-stones, a group of five pits were found, one of which was found to contain charcoal dating from between 469AD and 669AD.
This find may indicate that activity continued within the stone circle, perhaps even activity of a ritual nature, until well into the Iron Age and the middle of the first millennium AD.