From the World Heritage inscription:
The four castles of Beaumaris, Conwy, Caernarfon, Harlech and the attendant fortified towns at Conwy and Caernarfon are the finest examples of late 13th century and early 14th century military architecture in Europe, as demonstrated through their completeness, pristine state, evidence for organized domestic space, and extraordinary repertory of their medieval architectural form.
The castles as a stylistically coherent groups are a supreme example of medieval military architecture designed and directed by James of St George, King Edward I of England’s chief architect, and the greatest military architect of the age.
The extensive and detailed contemporary technical, social, and economic documentation of the castles, and the survival of adjacent fortified towns at Caernarfon and Conwy, makes them one of the major references of medieval history.
The castles of Beaumaris and Harlech are unique artistic achievements for the way they combine characteristic 13th century double-wall structures with a central plan, and for the beauty of their proportions and masonry.
There are several significant things about the castles of Edward I in Wales:
1) The castle and walls of Conway might be the best preserved medieval city walls in Europe. The only other walls I’ve seen which were this quality were in Dubrovnik, Croatia. You can walk almost the entire
2) Caernarfon Castle is currently the location where the Prince of Wales is crowned. The round platform in the photo is the location of the crowning ceremony.
3) The entirety of the castles were part of the final conquest of Wales by the English. Having difficulty conquering the Welsh, Edward I created a ring of castles in the north of Wales to surround the mountains making it difficult for the Welsh to kick the English out.
I found the castles to be perhaps the most interesting attraction in Northern Wales.
View my complete list of UNESCO World Heritage sites.