Built between 1283 and 1301, Caernarfon Castle was Edward I's most impressive stronghold — and the most expensive of his chain of North Welsh fortresses. The polygonal towers and colour-banded masonry were inspired by Constantinople's fifth-century walls, giving it a distinctly un-English look that set it apart from anything else in Britain.
It proved nearly impregnable in practice. In 1404, just 28 defenders held off Owain Glyndŵr's siege, and during the seventeenth-century Civil War it resisted three separate attacks.
Originally conceived as both a seat of government and a royal palace, the towers were fitted with ornate stained glass windows. The Eagle Tower is the finest surviving example of this ambition. Inside the Queen's Tower, you'll find a museum dedicated to the Royal Welsh Fusiliers, Wales's oldest infantry regiment. Other towers hold exhibits on Edward I's campaigns across Wales and the 1969 investiture of Prince Charles.
A UNESCO World Heritage Site, the castle today is managed by Cadw and well worth a couple of hours.