United Kingdom: Castles and Town Walls of King Edward in Gwynedd (1986)

The castles of Beaumaris and Harlech (largely the work of the greatest military engineer of the time, James of St George) and the fortified complexes of Caernarfon and Conwy are located in the former principality of Gwynedd, in north Wales. These extremely well-preserved monuments are examples of the colonization and defence works carried out throughout the reign of Edward I (1272–1307) and the military architecture of the time. Source: whc.unesco.org

Postcard 1: Harlech Castle

Thanks to Mia.

Postcard 2: Beaumaris Castle

Thanks to Ms Carol

Postcard 3: Conwy Casstle

thanks to Ms Anu.