An atrium is a large, open space inside a building, usually rising up through multiple floors with a ceiling of glass or skylights far above. Picture walking into a fancy hotel and seeing a vast central hall where you can look up several stories to a glass roof: that's an atrium. The open design lets natural light pour down through the building, making the space feel bright and impressive.

The word comes from ancient Roman houses, where the atrium was the central room open to the sky, often with a shallow pool to catch rainwater. Roman families received guests in their atrium, and it served as the heart of the home.

Modern atria (the plural of atrium) appear in museums, office buildings, shopping malls, and hotels. They create a sense of grandeur and help people orient themselves. Saying “Meet me in the atrium” gives everyone a clear central landmark.

In biology, your heart also has atria: the two upper chambers that receive blood before pumping it to the ventricles below.