A common design feature to many mid-century period modern houses, is the Atrium.
In architecture, an Atrium (plural: atria, or atriums) is a large open space located with a building. Atriums were a common feature in ancient Roman dwellings, providing light and ventilation to the interior.
Modern Atria, as developed in the late 19th and mid 20th centuries, are sometimes several stories high and have a glazed roof and/or large windows, and are often located immediately beyond the main entrance door(s), or in the center of the building.
Atriums have been popular because they give their buildings a natural feeling of space and light, and a sense of integration with the environment. They became a defining and popular feature in modernist residential architecture during the decades immediately following World War II, and although their popularity in residential home design waned during the 1980s and 1990s, a resurgent interest in modernism - and mid-century modernism - in residential architecture has sparked a renewed interest in them.
The Atrium is often covered by a glass roof (but sometimes open to the sky; in which case it is more accurately defined as a courtyard) that provides light and adds an extra space to live in, but with an 'outside" feeling, even during cold or rainy days.
A glass-ceilinged Atrium can serve as a greenhouse; the glass ceiling traps solar heat. In mid-century houses, Atriums often are the heart of a house and almost all, if not all, rooms are placed around them.
Considering how important the indoor-outdoor connection is for mid-century modernist design houses, Atriums are the perfect example. Sometimes used as covered gardens, sometimes as a gallery, and sometimes as an extension of the living area, every house owner chooses to use the Atrium with what fits his needs best.