Harlech Castle was one of Edward I's 'iron ring' of castles built during his second castle building campaign. It was designed by Master James of St George who personally supervised the construction.
Work began in 1283 and was completed in 1290. The castle was built on a rocky promontory overlooking Tremadoc Bay. It is a fine example of the concentric castle with outer walls giving further protection to the inner walls, which contain the main living quarters. The inner walls were defended a great gatehouse.
This remains the chief feature of the castle, dominating the quadrangle of the inner ward. The gatehouse by this period had taken over the function of the earlier keep and contained the main residential apartments. The entrance is a narrow passage protected by two portcullises and seven sets of 'murder holes'. Beyond the outer walls deep dry moats were hewn out of rocky crag on two sides of the castle and the back was protected by the sea cliffs. A fortified stairway led down to the sea allowing the castle to be supplied by ships if the land was blockaded.
In 1294 the Welsh rebel Madog besieged the castle but help duly arrived from Caernarfon and Conwy. However, in 1404 Owain Glyndwr blocked the land route whilst his French allies patrolled the sea below. After a long and bitter siege with no hope of relief the castle surrendered. Owain Glyndwr made the castle his stronghold from which to carry out the rebellion but after a similar siege in 1409 was forced to surrender to the English.
The castle's grimmest history occurred during the Wars of the Roses. The Castle was a Lancastrian stronghold under Dafydd ap Ieuan and his "Men of Harlech". After suffering great hardship the castle yielded in 1468 to the Yorkists under Lord Herbert, Earl of Pembroke. Dafydd was the last Lancastrian commander to surrender.
After this time the castle decayed, being used only as a prison for housing debtors. Even in a poor state of repair it withstood the Parliamentarian forces under Major-General Mytonn and in 1647 was again the last garrison to surrender. A demolition order after the Civil War was never carried out.
Today half a mile of gorse and dunes divide the castle from the sea.