Castell Bryn Gwyn

Castell Bryn Gwyn (also spelled Castell Bryngwyn) is a prehistoric site on the Isle of Anglesey, west of Brynsiencyn. It is a circular clay and gravel bank covered with grass, still some 1.5 metres (5') high and revetted externally by stone walls, which surround a level area some 54 metres (177') in diameter. Its name means "White Hill Castle".

Prehistoric origins
The original use of this site is uncertain although it may have been a religious sanctuary. Later Neolithic pottery indicates use in this period, and it may have been a henge monument at this time. The earliest bank and ditch belong to the end of the neolithic period (2500-2000 BC).

Roman invasion
During the Iron Age, the present wall was built, and it was rebuilt in Roman times and later.

Access
Car parking is minimal but the site is accessible from the A4080 by a footpath. Another path follows the low ridge, southwest over stiles to the Bryn Gwyn stones, or northeast, past the site of the former stone circle of Tre'r Dryw Bach, some ½ mile (800 metres) to Caer Lêb where it meets a minor road with limited car parking space.