Subterranean Courtyard

Quick answer：

A subterranean courtyard, also known as an underground courtyard or sunken garden, is a courtyard located below the ground level. It is often used in traditional Chinese architecture and can feature gardens, pools, or other natural elements. These courtyards provide a peaceful and secluded space within the urban environment. They are designed to maximize natural light and ventilation, often incorporating skylights or sunken wells.