Jersey Channel Islands
Built between 1328 and 1330.
Little is known about the history of this roughly built fort. Grosnez- meaning either 'big nose' in modern day Jersey/French Patois or "great headland" (from the Norse word 'ness') - was built to protect the islanders from the French. It was obviously not intended to withstand a siege as water would have to be carried from the nearest spring, 200 yards away. Additionally, there were no secondary walls inside the castle so once the outer walls were breached it's capture was certain.
The castle was captured in 1468 and by 1540 it lay in ruins.