Cantre’r GwaelodAccording to legend, Cantre’r Gwaelod was the rich and fertile ‘lowland hundred’ and sixteen cities governed by Gwyddno Garanhir, whose palace, Caer Wyddno, was reputedly near Aberystwyth. The land stretched across what is today the open sea of Cardigan Bay, and lay below sea level, protected by sea walls.
The guardian of the sea defences was Seithennyn, a friend of the king charged with the all important role of shutting the sea gates every night. One night Seithennyn, who liked his drink, was at a feast in the king's palace, and forgot to shut the sea gates. It was a stormy night and the high spring tides broke through, quickly flooding Cantre’r Gwaelod, and forcing its people to flee to the hills.