This ancient archway
has stood guard over the edges:
coastline guarding sea.
Conwy Castle and Conwy Falls are nowhere near each other. So don’t go to Conwy looking for the Falls because they are actually near Betws-y-coed. Otherwise, Conwy Castle sits solidly above the mouth of a river/harbour, filled with arching windows and doors, with turrets and watch points high above the river, reached from the narrowest curved staircases.