Castles in Middle English Arthurian romance may vary from Malory's generally undifferentiated ‘fair’ castles to the Gawain-poet's splendid Hautdesert, which is as real as the castles at Windsor and Carlisle and as ideal as those in Gothic illuminations, with their pink stone walls, azure pinnacles, and gilded gables. Whenever it appears in romance, the castle is a hierarchic image implying the existence of a mythic aristocratic society unhampered by the constraints of everyday life. The realistic aspects are drawn from contemporary models. The supernatural aspects are likely to reflect motifs in Celtic tales of heroes’ journeys to the Otherworld.

When the hero of Sir Orfeo, a Middle English metrical romance (c.1300), follows a cavalcade of splendid ladies through a rocky barrier, he emerges into a brilliantly lit green plain dominated by a crystal castle. Its hundred towers are wonderfully high, its buttresses pure gold, its vaulting elaborately enameled, its spacious apartments radiant with precious stones, its poorest pillar of burnished gold. No man might describe or imagine ‘the riche werk that ther was wrought’. The formulaic combination of crystal, gold, and jewels in a castle of consummate beauty and brilliance indicates that Sir Orfeo has entered a fairyland of marvelous beauty.

The Otherworld journey is an archetype of early Irish literature. Teigue Mac Cian, traveling across the seas, finds a silver fortress with posts of burnished gold, corridors of varicolored marble, a silver-floored hall with golden doors and diamond-studded walls. Finn and his companions, accepting the invitation of a supernatural host to enter his sidh (a faerie mound), are greeted by a hospitable company seated on crystal benches. They are entertained with harp music played by the host's beautiful daughter, served the newest meat and the oldest liquor, and given a marvelous cup that produces whatever drink is desired. An essential part of the happy Otherworld is the beautiful, generous fée who is all too willing to become a mortal's mistress. Ruad Mac Rigdon not only enjoys making love to nine gorgeous girls on nine successive nights but also receives from each one a golden cup as his reward. The sacrifice involved in returning to the natural world is expressed by Dunlang O'Hartugan just before the Battle of Clontarf: