n.
In an ancient Roman house, an open central court that contained the impluvium, a basin where rainwater collected.
It originally contained the hearth and functioned as the center of family life. The term later came to be used for the open front courtyard of a Christian basilica , where congregants collected before services. The atrium was revived in the 20th century in the form of glass-covered, greenery-filled multistory spaces sometimes found in shopping centers, office buildings, and large hotels.
Atrium of the basilica of S. Ambrogio, Milan, 10881128
Alinari
Art Resource