Stonehenge 3 VI
Two further rings of pits were dug outside the outermost sarsen circle, called the Y and Z Holes. The Z holes were about 2m outside the outermost sarsen circle and the Y holes about 5m further out. These were each of thirty pits and each seems to match with one of the uprights in the outer sarsen circle. They were never filled with stones however and were permitted to silt up over the next few centuries; their upper fills contain Iron Age and Roman material. Monument building at Stonehenge appears to have ended around 1600 BC.