An adjacent Sound, running between Mainland, and Burray, is named after Holm. It has since been blocked up by the Churchill Barriers. The parish flanks the north side of the Sound and extends to within 2½ miles of Kirkwall, and contains the village of St Mary's Holm, as well as the island of Lamb Holm. The Mainland section is six miles by two.
The shores are mostly rocky, and the interior consists of light thin, loamy land.
Netherbutton Radar Station, which was part of the Chain Home system, was situated on both sides of the A 961, although little now remains except four concrete mast bases. Its construction was supervised by Leonard Chapman, who then held the rank of corporal.