Valley or Dyffryn or Y Fali
The name is thought to derive from Telford's engineering works when constructing this section of the A5 trunk road. It is now commonly associated with the nearby Royal Air Force base, where recruits, including Prince William of Wales, undertook training in flying techniques, and search and rescue.
The RAF station is also the base of C Flight, 22 Squadron Search and Rescue. In addition, Anglesey Airport, Maes Awyr, operates from here.