Originating from the early 12th century, the visible structure of Llanblethian is from early 14th century. The site overlooks the River Thaw set on a steep spur. There are remains on a stone curtain wall with a massive twin towered gatehouse, a corner tower and ruined keep. The gatehouse was used as a prison in the 16th century, but was in ruins by the 18th century. The castle itself is rectangular in shape but the lack of an inner bailey proved to be a weakness that limited its usefulness and longevity as a fortress.

~ History ~

1102 - Robert Fitzhamon, the first Norman Lord of Glamorgan bequeaths the lands of Llamblethian as a lordship to Herbert de St Quentin, who sets about the building of a timber ringwork castle, defended by banks and ditches.

1233 - Richard Siward seizes the lordship from the Fitzhamon's.

1245 - The powerful and influential Marcher Lord Earl Richard de Clare seizes Llamblethian from the Siward's, along with swathes of South Wales.

1307 -  Gilbert de Clare gives orders for the building of a new powerful gatehouse for the Castle.

1314 - De Clare is killed at the Battle of Bannockburn. The castle still incomplete.

1741 - The castle is recorded as ruinous.