There are other prehistoric geographic features, but the specific age or time period is unclear. The Bolster Bank, or Bolster & Chapel Bulwark, at Porth, is an univallate earthen boundary about  long.
Other prehistoric geographic features are present, though their specific age or era is unclear. At Porth, the Bolster Bank, or Bolster & Chapel Bulwark, is a univallate earthen boundary roughly in length.