The appearance of this 'passage grave' is rather deceptive.
Today it is open to the elements, but originally it took a different form. The central chamber had a domed-shaped roof that rose to around three and a half metres. This was built entirely of overlapping stones, sealed by a single large slab.
The passage leading to the chamber was covered by lintels and so low that people would need to crawl along it.
For most of the time the chamber and passage were dark, but they are carefully and deliberately aligned on the midwinter solstice. On the shortest day of the year the rear of the chamber is illuminated by the setting sun. Towards the back of this cairn particular use was made of quartz which would be illuminated by the rising sun. The monument probably contained burials but the record is rather confused.
The foundation course of the chamber is not of even height.
It is lower towards the rear and higher towards the enrtrance. The same applies to the kerbstones which support the edges of the cairn. They seem to have been selected for their colour and texture and one of them is decorated with abstract designs.
After a short interval the tomb was closed.
A bank of rubble was piled against the kerb and prevented access to the passage. At the same time the cairn was enclosed by a ring of standing stones, also graded by height. The tallest monoliths are by the entrance.
-from the Historic Scotland Information Board