Dinorwig

 This postcard was sent by Adam

Pontcysyllte Aqueduct

 This postcard was sent by Anu

Caernarfon, Conwy, Beaumaris and Harlech Castles

 This postcard was sent by Tündi

South Stack Lighthouse

 The South Stack Lighthouse is built on the summit of a small island off the north-west coast of Holy Island, Anglesey

The Ugly House, Betws-y-Coed

 I don't know why this is called the Ugly House, it doesn't seem that ugly

Beaumaris Castle

 This is one of the Castles and Town Walls of King Edward in Gwynedd

Blaenavon Ironworks

 This postcard was sent by Stella