Annwfn is also the name of a land under waves or over sea, called also Caer Sidi, “the revolving castle,” about which “are ocean’s streams.”  It is “known to Manawyddan and Pryderi,” just as the Irish Elysium was ruled by Manannan.[1249] Another “Caer of Defence” is beneath the waves.[1250] Perhaps the two ideas were interchangeable.  The people of this land are free from death and disease, and in it is “an abundant well, sweeter than white wine the drink in it.”  There also is a cauldron belonging to the lord of Annwfn, which was stolen by Arthur and his men.  Such a cauldron is the property of people belonging to a water world in the Mabinogion.[1251]

The description of the isle of Avallon (later identified with Glastonbury), whither Arthur was carried, completes the likeness to the Irish Elysium.  No tempest, excess of heat or cold, nor noxious animal afflicts it; it is blessed with eternal spring and with fruit and flowers growing without labour; it is the land of eternal youth, unvisited by death or disease.  It has a regia virgo lovelier than her lovely attendants; she cured Arthur of his wounds, hence she is the Morgen of other tales, and she and her maidens may be identified with the divine women of the Irish isle of women.  Morgen is called a dea phantastica, and she may be compared with Liban, who cured Cuchulainn of his sickness.[1252]

The identification of Avallon with Glastonbury is probably post-pagan, and the names applied to Glastonbury—­Avallon, Insula Pomonum, Insula vitrea—­may be primitive names of Elysium.  William of Malmesbury derives Insula Pomonum in its application to Glastonbury from a native name Insula Avallonioe, which he connects with the Brythonic avalla, “apples,” because Glastenig found an apple tree there.[1253] The name may thus have been connected with marvellous apple trees, like those of the Irish Elysium.  But he also suggests that it may be derived from the name of Avalloc, living there with his daughters.  Avalloc is evidently the “Rex Avallon” (Avallach) to whose palace Arthur was carried and healed by the regia virgo.[1254] He may therefore have been a mythic lord of Elysium, and his daughters would correspond to the maidens of the isle.  William also derives “Glastonbury” from the name of an eponymous founder Glastenig, or from its native name Ynesuuitron, “Glass Island.”  This name reappears in Chretien’s Eric in the form “l’isle de verre.”  Giraldus explains the name from the glassy waters around Glastonbury, but it may be an early name of Elysium.[1255] Glass must have appealed to the imagination of Celt, Teuton, and Slav, for we hear of Merlin’s glass house, a glass fort discovered by Arthur, a glass tower attacked by the Milesians, Etain’s glass grianan, and a boat of glass which conveyed Connla to Elysium.  In Teutonic and Slavonic myth and Maerchen, glass mountains, on which dwell mysterious personages, frequently occur.