The Inner Courtyard of the upper castle, decorated between 1564 and 1567 with grisaille painting al fresco (grey painting on still-wet plaster), is among the best-preserved examples of fresco from the sixteenth century. The representations of princely virtues and muses, female and male heroes, and diverse heroic acts sought to display the royalty as exemplary. They relate to their commissioner Archduke Ferdinand II, patron of the arts and host of lavish festivities.
Aided by its uniform decorative system, the painting also fulfils the architectonic role of unifying the irregular courtyard and compensating for the steep and narrow character of the space. Comparable illusionistic architecture with painted windows, sculptures, cornices, and perspective foreshortening can be found from the fifteenth century onward in northern Italy, for instance the Pescheria Vecchia in Verona painted by Andrea Mantegna in 1464.
In form and content, the scheme of the Ambras courtyard can be related to Litomyšl castle, the palace of the archbishop of Prague at Horšovský Týn, and Palais Martinitz in Prague. Engravings by the artists Virgil Solis and Jost Amann were used as the models both for the sites in Bohemia and for Ambras.
The ground level is articulated with painted diamond-pointed blocks. The most striking scenes are depicted on the west wall: a Bacchic procession with carts, satyrs, and bacchantes between the first and second floors, and Orpheus playing music before the animals between the second and third floors.
On the north wall (to the right of the entrance) allegories of the liberal arts – music, geometry, arithmetic, astronomy, grammar, dialectic, and rhetoric – stand in architectural niches between the windows of the first floor, above which the Bacchic procession continues. At the level of the second floor, an interruption in the painted decoration marks the location of a loggia during the Ferdinandine period, which was removed in the nineteenth century. To the west of the boundary with the loggia, the remains of the original coloured painting are evident on an earlier plaster layer. The battle scenes and knights in the upper rows are no longer identifiable.
The east wall shows a trompe-l’oeil window with a stag at the ground level, while Old Testament heroines such as Judith, Esther, and Yael appear above; over the Bacchic procession between the first and second floors are unidentifiable female figures, Judith with the head of Holofernes, a battle scene, and knights in fantastic armour.
The south wall (to the left of the entrance) depicts the virtues of fides (faith), spes (hope), caritas (charity), justitia (justice), prudentia (prudence), fortitudo (fortitude), temperantia (temperance) und sapientia (wisdom) between the windows of the first floor, surmounted again by the Bacchic procession, while above are probably the nine muses, heroes from antiquity and a battle; the ‘new heroes’ Alexander the Great, Godfrey of Bouillon, David, Arthur, Charlemagne, Judas Maccabeus, Joshua, Hector, and Julius Caesar are shown at the top.