The Preseli Hills or Preseli Mountains are a range of hills in north Pembrokeshire, West Wales. They form part of the Pembrokeshire Coast National Park. The hills rise to 536 metres above sea level at Foel Cwmcerwyn and are dotted with prehistoric remains, including evidence of Neolithic settlement. In 1923 the petrologist Herbert Henry Thomas identified that bluestone from the hills corresponded to that used to build the inner circle of Stonehenge , and more recent geologists have identified Carn Menyn, sometimes called Carn Meini, as one of the bluestone sources. Others theorise that bluestone from the area was deposited close to Stonehenge by glaciation. Slate quarrying was once big business in the Preseli Hills, and remnants of the quarries can still be seen in Rosebush, Pembrokeshire. There is still a slate workshop at Llangolman where authentic Welsh slate is still used in a variety of craft items.