A sunken courtyard in a villa design typically refers to a courtyard that is below the ground level of the villa. This design feature can provide privacy, enhance the aesthetic appeal of the property, and create a unique outdoor space. The design drawing would include details such as the layout of the courtyard, the placement of windows and doors, and integration with the surrounding garden or outdoor areas. This type of design is often favored in modern residential architecture for its versatility and aesthetic qualities.