A sunken courtyard in a villa refers to a courtyard that is situated below the level of the main building. This design feature often provides a private, secluded space that can be used for relaxation or gardening. Design plans for such a courtyard typically include details on the layout, landscaping, and architectural elements such as steps, walls, or bridges that connect the sunken area to the main building or the surrounding garden. These plans are essential for ensuring the functionality and aesthetic appeal of the space.