Hulbjerg megalithic passage crypt, Langeland, Denmark (c. 3000 BCE).

Excerpts from — Matt Gatton, “The Camera Obscura and the Megalithic Tomb: The role of projected solar images in the symbolic renewal of Life.” Originally posted March 9, 2010.


In the Neolithic, a wide range of peoples expended incredible effort to erect large stones, or megaliths. A boulder built Passage Crypt was covered with an earthen mound and characterized by a long passage that led to a subterranean chamber. Newgrange in Ireland and Maeshowe in Scotland are the most renowned examples, although there are hundreds of others around the world.


Ghostly image of a man projected onto the backstone of the chamber at the Grønhøj megalithic crypt, Rugballegård, Horsens, Denmark. (M. Gatton)

To control access to the chamber, the passages could be closed or opened. Passages were sealed by various methods (boulders, slabs, blocks, or wooden elements) that left purposeful apertures for the sunlight to penetrate the chamber. Archeo-optical research suggests the objective of the ritual was not the light itself, but the images it carried.

Three distinct types of images where possible: solar, monumental, and spirit.


Solar Images


Cairn T at Sliabh na Callaigh at Loughcrew, Ireland orients toward the equinox sunrise. On March 21st sunlight shines through the passage and illuminates the backstone of the rear recess. As the sun rises, angling upward and toward the south, a broad area of light slowly moves over the backstone from upper left to lower right. Circular solar pictographic engravings on the backstone demarcate the diagonal movement of the light across the stone. These circles specifically chart the sun’s course and so document the procession of a solar disc, proving that it was an image of the sun, not just generalized light, projected inside.




TLC1                 TLC2                  TLC3

Monumental Images

Megalithic monuments often come in clusters with sight lines from monument to monument. The small apertures that projected the image of the sun into the chambers during the direct alignment would also project images of distant mounds or standing stones when the sun was in the opposite quadrant, the reverse alignment.

Spirit Images

spirit chamber

Between the direct alignment and the reverse alignment is a window of time when the entrance to the chamber would fall ever so slightly into shadow while the area directly in front of the passage would still be bathed in full sunlight. At this point the mound became a spirit chamber.

A shaman ushers a dozen people through the cloaked entrance of the tomb. They crawl down the passage way into its dim womb where they huddle in fear and hope. Candlelight flickers across the faces and stones as the lore is told. The shaman extinguishes the candle. The shaman’s confederates outside uncover a hidden hole in the entrance cover and ‘magically’ the image of gods and elders ‘emerge’ from the backstone (really the projected image of bedecked shamans’ assistants outside). Exultations and lamentations arise in the darkness, tears and song, for here is what it means to die and learn what lays beyond the mortal veil. Attendees lay hands on the spirits on the backstone, connecting to the sky above and to those below, touching the eternal and indomitable. Through the spirits they gain a piece of immortality and a peace for their own mortality. The image brings the promise that they will be reunited with the others that have gone before.

To learn more about image projection in megalithic monuments, see the remarkable fieldwork from Bryn Celli Ddu, Cuween Hill, Wideford Hill, Vinquoy Hill, the Dwarfie Stane and the Grey Cairns of Camster directed by our colleague Dr. Aaron Watson in the United Kingdom.

Please visit his website at:

Or read his most recent publication on the topic:

Watson, A. and Scott, R. (2016). “Materialising Light, Making Worlds: Optical Image Projection within the Megalithic Passage Tombs of Britain and Ireland.” In The Oxford Handbook of Light in Archaeology (Papadopoulos, C. and Earl G., eds.) Oxford: Oxford University Press.