Approx. 1700 BC two other rings with holes were dug outside the stone circle. These are known as Y and Z Holes (11 a.m. to 12 p.m.). The concentric circles of 30 holes were never filled with stones. The monument of Stonehenge in England appears shortly thereafter, around 1600 BC to have been abandoned. The holes were filled in the next few centuries, the upper layers of fillings contain materials from the Iron Age.