First-level sunken courtyard effect

Quick answer：

The first-level sunken courtyard effect refers to the design of a courtyard that is sunken below the ground level of a building. This architectural feature is often used in traditional Chinese gardens and modern residential buildings. It creates a sense of depth and privacy, and allows for the integration of greenery and water elements. The sunken courtyard can be accessed through a staircase or a bridge, and is typically enclosed by walls or hedges, providing a serene and secluded space within an urban environment.