Sunken courtyard on the first floor drawing

Quick answer：

A sunken courtyard on the first floor refers to a garden or courtyard that is lower in elevation than the surrounding area, creating a level or sunken space on the first floor of a building. This architectural feature can provide a more private or secluded outdoor space, often used for relaxation or landscaping. Sunken courtyards are commonly found in traditional Asian architecture and can also be seen in modern designs for their aesthetic and functional benefits.