|Notes:||One of three known chambered cairns in Papa Westray and described by Davidson and Henshall as “an extraordinary chamber with a total length of 20.4m and fourteen cells.” |
The cairn, which sits at the highest point of the island, was investigated in 1849 , but left unprotected until it was taken into Guardianship in 1930. By this time the walls had been considerably reduced and the interior filled with debris.
Orientated NNE to SSW, the sub-rectangular cairn measures c38 by 19.5m and survived to height of 3m when a concrete roof was added in the 1930s.
The chamber measures 20.4 metres in length, comprising three areas. The central area is is 13.5 m long with extensions, separated by roof height walls, at each end. The south-western chamber is 3.4m long while the north-eastern is 2.2m long.
The width of the chamber varies from 1.2m and 1.4m.
When opened in the autumn of 1849, by Lieutenant F. W. L. Thomas, the commander of the Royal Navy survey ship Woodlark, the chamber walls stood up to 2.7m high. The long walls rose vertically for about 1. 5m above which they oversailed to reduce the space between them to 0.8 m. Part of the roofing by transverse lintels had also survived. 
Thomas discovered 14 side cells which were accessed by 12 entrances in the walls of the chamber – two of which lead to double cells. There were three entries on each side of the main chamber, and one on each side and one at the end of the two chamber extensions.
The cell entrances vary from about 0.4 to 0.6 m wide and about 0.4 to 0.6m high, and are mostly roofed by large lintels 1. 1 m or more long by 0.15 to 0.45 m thick. The cells measure between 1.2 and 1.6m wide by between 0.8 and 1.1m from back to front, and from 1. 1 to 1.7 m high. They are roofed with flat slabs except in the south-western cell which is by slabs set on edge.
According to Thomas “[n]o implements or organic remains were found” other than some animal bone, which he considered to be quite recent.
In the 19th century, Orkney antiquary George Petrie recorded that some of the cells had been deliberately filled with rubble mixed with bones to above the level of their entrances. 
Access to the interior was by a passage in the middle of the cairn’s ESE side.
Thomas recorded that the passage was 5.5m long and 0.8 m high “roofed by large flagstones, most of which are placed on edge, while some are horizontal”. 
Presently passage is 9.1m long, of which the inner 3.8m is roofed and original (except that the outermost lintel may be a replacement), but the outer 5. 3m, which curves slightly to the east, has been partly reconstructed and is without lintels. The extent of the 1931 reconstruction and the evidence on which it was based have not been recorded.
The passage measures 0.6m hight and 0.5m wide. A large upright block in the northern wall, 2m outside the lintelled section, may have marked the end of the passage as recorded by Thomas. 
On either side of the entrance, Thomas traced a wall-face for a short distance standing 0.6 to 0.9m high. It lay about 5. 5m from the chamber and perhaps represented the original outer edge of the cairn.
During his exploration, Thomas also came across incised markings on the chamber walls:
“[O]n the side wall near the entrance, and about 6 feet from the floor, there is a neatly engraved circle about 4 inches in diameter; there is also another stone with the appearance of having two small circles touching each other engraved upon it; but it is so common, to find geometrical figures upon the Orkney flags, from a semi-crystallization of the pyrites which they contain, that I am unable to decide whether those seen in the Picts’ house are natural or not.” 
Prompted by Thomas’ account, Petrie visited the remains, around 1854, to investigate further:
“I carefully examined the walls of the main chamber and of the square chamber at each end, and was agreeably surprised not only to find the circles referred to by Lieut. Thomas, but also to discover quite close to them, as well as on various other stones in the walls, other engraved figures.
“One set is on a large lintel over the entrance of the passage between the south chamber and the small cell on its east side. The thorough washing of tie walls, by their exposure to the weather since Lieut. Thomas cleared the rubbish out of the chambers, has left the engraved figures on the stones quite distinct, and it is easy to see that they have been formed by a pointed instrument tolerably sharp.” 
Thirty-four areas of possible marking or decoration have now been identified within the structure. 
Holm of Papa Westray South