Castell Bryn Gwyn

Castell Bryn Gwyn ("White Hill Castle") is a prehistoric enclosure on the Isle of Anglesey, west of Brynsiencyn. Originating as a late Neolithic henge (c. 2500-2000 BC), excavations in 1959-60 revealed it was later adapted as a defended settlement. The circular clay and gravel bank, still 1.5 m high and revetted by stone walls, encloses an area 54 m in diameter. Finds of pottery, post holes, and flint and bronze tools confirmed habitation rather than purely ceremonial use. The stone wall was rebuilt in the Iron Age and again in Roman times, with pottery dating to the late 1st century AD.