Caernarfon castle was constructed at Caernarfon in North Wales by King Edward I of England, following his successful conquest of the principality. His son, later Edward II of England was born here in 1284.

The castle is one of several stone castles built by King Edward to help subdue the Welsh, but is probably his supreme achievement. Its concentric design is sophisticated by comparison with earlier British castles, and the walls are said to have been modelled on those of Constantinople, Edward being a keen crusader. The castle dominates the Menai Strait, which had been of great strategic importance during Edward's Welsh campaigns.

The castle was used in 1911 for the investiture of the then Prince of Wales, the future Edward VIII of the United Kingdom, because of its past associations with the English crown. This set a precedent which was to be repeated in 1969 with the investiture of the present prince.

The castle also houses the regimental museum of the Royal Welch Fusiliers.