The Callanish Standing Stones were erected around 5,000 years ago, making them significantly older than Stonehenge and the great pyramids of Egypt. Perched on a prominent ridge, easily visible from land and sea for miles around, they are set out in a cross-shape, with avenues spreading out from a central ellipse that align with the path of the sun and the moon at different points in the solar cycle. 

This has given credence to a theory that they were used as some form of astronomical observatory. Also known as the Calanais Stones or Callanish I, there are at least 11 smaller stone circles erected in the vicinity of the mysterious Neolithic structure.