Roman courtyards, also known as atria, were an important part of Roman architecture. They were open-air courtyards surrounded by a roof and walls, often with a pool or fountain in the center. Atria were used for social gatherings, religious ceremonies, and other activities. They were also used to provide light and ventilation to the interior of the building. The term atrium comes from the Latin word for 'entry hall' and was used to describe the central courtyard of a Roman house.