Edward I finished this intimidating yet spectacular building in 1289, the southernmost of his 'iron ring' of fortresses designed to keep the Welsh firmly beneath his boot. The grey sandstone castle's massive, twin-towered gatehouse and outer walls are still intact and give the illusion of impregnability even now. A new visitor centre, with interactive displays, kids' activities and films, was opened in 2015, where the Castle Hotel once stood.

A drawbridge leads through the gatehouse to the compact inner ward, where four gloomy round towers guard the corners. Some of the ramparts are partly ruined and closed off, but you can climb up other sections for views in all directions. The fortress' great natural defence is the seaward cliff face. When it was built, ships could sail supplies right to the base.

Despite its might, this fort­ress has been called the 'Castle of Lost Causes' because it has been lucklessly defended so many times. Owain Glyndŵr captured it after a long siege in 1404. He is said to have been crowned Prince of Wales in the presence of envoys from Scotland, France and Spain during one of his parliaments in the town. He was, in turn, besieged here by the future Henry V.

During the Wars of the Roses the castle is said to have held out against a siege for seven years and was the last Lancastrian stronghold to fall. The siege inspired the popular Welsh hymn Men of Harlech, which is still played today in regimental marches and sung with patriotic gusto at rugby matches. The castle was also the last to fall in the English Civil War, finally giving in to Cromwell's forces in 1647.

The finest exterior view of the castle (with Snowdon as a backdrop) is from a craggy outcrop on Ffordd Isaf, opposite Maelgwyn House.