The castle's most distinctive feature is its Italian-influenced courtyard façade, which forms part of the north range. Francis Stewart, the designer, had travelled to Italy, and was inspired by new styles and technology in buildings there, particularly the Palazzo dei Diamanti in Ferrara (c. 1582). This was the source of the diamond rustication on the courtyard wall. The initials of Francis and his wife Margaret Douglas appear on the walls, together with an anchor representing Stewart's position of Lord High Admiral of Scotland. Inside are further innovations: Scotland's first "scale-and-platt" stair, "i.e." a modern-style staircase with landings; and a drawing room to the north of the old tower.