Pen-y-Mwd Mound is a sub-circular flat-topped earthwork motte but nothing is known of its early history. On the south side of the steep sided mound are traces of the surrounding ditch and to the south-east are the characteristics of a possible bailey. South-eastern excavations adjacent to the motte, have found the stone foundations of a possible 13th century defensible hall house. Having had a number of alterations, its final 14th century form was a winged three-unit hall house. Interestingly Y-Mwd in early Welsh means vault or chamber, so the motte with its possible princely court or llys, could stand on a 5th or 6th century ceremonial site. 5 miles west is Penrhyn Castle.