Bryn-y-cwn is a large earthwork motte, which has no recorded history. Standing at the northern end of a spur, the circular motte still retains three southern ditches. Possibly the fortress recorded as being 'palisaded' in 1244 but the site of the bailey has been lost. The castle could be the predecessor or an outpost of the stone castle at Flint but its dense cover of trees, makes it best viewed in winter. 5 miles north-west is Holywell Castle Mound.