The Lowland Hundred

Cantre'r Gwaelod, also known as Cantref Gwaelod or Cantref y Gwaelod (Welsh for 'The Lowland Hundred'), is a legendary ancient sunken kingdom said to have occupied a tract of fertile land lying between Ramsey Island and Bardsey Island in what is now Cardigan Bay to the west of Wales. It has been described as a "Welsh Atlantis" and has featured in folklore, literature, and song.