About a mile to the north-west of the Ring of Brodgar, is the site of what appears to be another prehistoric henge - the Ring of Bookan.

This massive earthwork comprises an enclosing ditch surrounding an oval raised platform, measuring about 44.5 metres by 38 metres.

The interpretation of the Ring of Bookan is not clear, although a recurring suggestion in the past was that it housed a Maeshowe-type cairn. Other suggestions are that the enclosed platform once featured a series of standing stones, or a cairn.

The dimensions of the Bookan "ring", however, hint at a connection with the nearby Standing Stones of Stenness.

At two metres deep and 13 metres across, the Bookan ditch is wider than the ditches found at both Brodgar and the Standing Stones, but similar in depth to the Stenness henge. The enclosed area of the Ring of Bookan is also almost identical to that of the Stones of Stenness.

The Bookan henge lacks two features common to Brodgar and Stenness - an entrance causeway and outer bank. These, however, could easily have fallen victim to ploughing and farming over the centuries.

Within the ditch are a number of stones and a rough mound. It has been suggested that this is the remains of a cairn, but this remains speculation.

Photographs of the Ring of Bookan