On the cliffs at Les Landes, at the most north-westerly point of Jersey you can find the ruins of Grosnez castle, 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, local legend has it that much of the stone was used to build St. Ouen's Manor. What is known is that locals took down the castle deliberately and used the stones on their own land particularly around the Mont Mado area of St. John from where the stone originally came. What remains today is a gatehouse separated from the mainland by a big ditch and a section of wall. Grosnez Castle is on public land so you can visit it anytime and the sunsets here are breathtaking.
To the south is Le Pinnacle, a 200 foot high rock, which was as an object of worship and a ceremonial site for thousands of years.