Licat Amr
An earthen mound at Archenfield which marked the burial place of Arthur’s son, Amr. It’s close to a fountain in Ercing (Archenfield). According to Nennius, Arthur buried Amr here after killing him.
Every time someone measures the burial mound, Nennius claims, he measures a different length.
Sometimes six, sometimes nine, sometimes twelve, sometimes fifteen feet.
Source
Historia Brittonum | Probably Nennius, early 9th century