The Grail Castle occupies a distinctive position in the depth-psychological corpus as one of the richest convergences of mythic symbolism, psychological transformation, and medieval spiritual imagination. The term designates not merely a narrative location within the Arthurian Parzival cycle but a charged symbolic threshold—the site where the hero’s capacity for compassionate questioning, or failure thereof, determines the fate of a wounded king and a wasted land. Jung himself dreamed of the Grail Castle and recorded the vision in ‘Memories, Dreams, Reflections,’ treating it as a living psychic inheritance, particularly in England, and interpreting the Grail’s absence from the castle as a task requiring solitary heroic effort. Von Franz elaborates Jung’s dream to emphasize the vessel’s alchemical lineage—from Zosimos through medieval mysticism—while Campbell provides the most expansive structural readings, situating the Castle as the locus of a reciprocal enchantment alongside the Castle of Marvels, and tracking its symbolic apparatus across Chrétien de Troyes, Wolfram von Eschenbach, the Cistercian Queste, and Wagner. A persistent tension in the corpus concerns whether the Castle represents a Christian, Gnostic, alchemical, or autonomous-psychological mystery. Wolfram’s version, emphasizing the neutrality of the wound’s origin and the castrate Klingsor as the real source of spiritual desolation, stands in sharp contrast to Wagner’s Manichaean polarization and the Cistercian monks’ ecclesiastical allegory. Greene reads the Castle’s Fisher King through the lens of Leo psychology and the wounded-father archetype. Together these voices render the Grail Castle the supreme image of blocked transformation in Western mythological psychology.