Hi, Susan. The ring's been known for centuries, and many of the stones are missing - taken for building work on nearby crofts. There was once a complete circle of sixty monoliths, but more than a third are gone, and a few more have fallen. The holes where the missing stones are can be easilly traced, though. As with Calanais in Lewis, the stones are not of equal hieght, varying from five - eleven feet. Again, as with Calanais, there are larger stones to mark the midsummer and midwinter observations. An avenue of small stones leads from the site.....only recently this was found to connect with the complex of at least fifteen stone buildings, some of them as large as a modern day badminton court, which have been located at the Ness of Brodger - a strip of natural causeway which links the circle to yet another, slightly smaller, circle. Latest carbon dates put the foundation of work at the Ness to around 3700 BC, making it at least nine centuries older than the earliest structures at Stonehenge.