Most of the play is set in Vermandero’s castle, a place of winding passages, secret meetings, and murderous acts. Vermandero’s castle is a sign of Vermandero’s noble place in society, symbolizing his strength and wealth. It is a grand abode and sparks the interest of both Alonzo and Alsemero. However, the castle’s stately exterior hides interior moral corruption. These two men are both lured inside the castle by its impressive reputation as well as their desire for Beatrice. Once inside the castle, they face tragic fates: death for Alonzo, who later haunts the castle; and betrayal for Alsemero, who marries an adulterous bride, spends his wedding night with her waiting-woman in disguise, and loses both women by De Flores’s hand. In part, the castle parallels Beatrice. While her virtuous, upper-class beauty attracts multiple suitors, she transforms to “ugly whoredome” (5.3.198) as her crimes are exposed.

The castle also symbolizes Beatrice’s sense of confinement and moral descent into sin. Beatrice lives within her father’s castle’s walls, just as she must live by his command and within patriarchal society more broadly. Beatrice tries to exercise agency within these confines: She convinces her father to invite Alsemero into the castle so she can scheme a way to marry him, and she orchestrates murders with De Flores’s help to avoid a marriage she does not want.