Negative one floor sunken courtyard effect

Quick answer：

A sunken courtyard, also known as an underground courtyard, is a design feature where a courtyard is situated below ground level. This creates a unique, secluded space that can be used for various purposes such as gardens, lounging areas, or even dining. The effect of a negative one floor sunken courtyard is that it adds a sense of depth and privacy to the property, often giving it an elegant and sophisticated appearance.