CaernarfonCaer‧nar‧fon, Caernarvon /kəˈnɑːvən $ kɑːrˈnɑːr-/a small town in northwest Wales, known for its castle where the British king or queen’s oldest son is given the official royal title, Prince of Wales. Prince Charles’s investiture (=ceremony for receiving this title) took place there in 1969.