On a narrow isthmus between the Lochs of Harray and Stenness, and by the road from the Stones of Stenness and the Ring of Brodgar, stands a large monolith known as the Watch Stone.

This stone is ninteen feet tall, five feet wide and just over a foot thick.

The stump of a second stone was found nearby, and in such a position that it is possible that these two stones formed part of yet another stone circle that was lost when the sea level (and hence the level of the Loch of Stenness, which is open to the sea) rose.