Harlech Castle sits on a clifftop above the small town and has the most dramatic position of any medieval castle in Wales: Snowdon and the Rhinog mountains filling the eastern skyline, the Llyn Peninsula and Cardigan Bay to the west. Built by Edward I in the 1280s as part of his Welsh conquest programme, it is now a UNESCO World Heritage Site.
The castle is compact, you can walk the walls in 20 minutes, but the views in every direction are worth far longer. The concentric fortification design, with the gatehouse as the primary defence, was innovative for its time and is still immediately readable in the structure.