Atrium

(1) In an ancient Roman structure, the atrium was the inner courtyard of a house, left open to the sky, usually having a pool for the collection of rainwater.

(2) In the 20th century, the word has been adopted to describe dramatic enclosed glass-roofed indoor spaces associated with high-rise office buildings and hotels.

(3) In Christian churches, the atrium is a courtyard flanked by porticos.