The north "rear" wall of the main chamber.
The walling inside Grain is almost all vertical with little evidence of the
gradual corbelling we are used to seeing in megalithic structures. Here, above
the walling,
we see the arrangement of overlapping large slabs that reduces the roof span and
transfers the load to the pillar supports.
Note the water-worn appearance of all of the roofing stones and the contrast
with the sharp-edged stones used for the walling, we noticed that this division
of
texture was continued throughout the entire souterrain.