Bryn y Cwn Motte is a large earthwork motte and bailey fortress, which has no recorded history. Standing at the northern end of a ridge, the circular motte still retains the southern part of its ditch and beyond this ditch is a sloping triangular platform, which could be the site of a bailey. The castle could be the predecessor or an outpost of the stone castle at Flint but the mottes dense cover of trees, makes it best viewed in winter. 5 miles north-west is Holywell Castle.