All 3 Uses

atrium
in
White: The Great Pursuit
(Auto-generated)

They crossed an atrium that rose all five stories and featured a large fruit tree at its center.†
Chpt 10
They entered through large double doors into an atrium, empty except for an ornately carved black desk and yet one more of the bronze statues of Teel eh.†
Chpt 13 *
Woref stepped across the room, entered the atrium, and gazed at the stairs that rose from floor to floor, up to the fifth where Chelise's room waited in silence.†
Chpt 15

Definitions:

(1) (atrium as in: atrium of the building)
a central open space in a building -- often a large skylit hall near the entrance

In ancient Roman houses and early Christian churches, an atrium was an open courtyard. In many modern buildings, it is an indoor space that may include plants, water features, and balconies or walkways to other rooms.
(2) (atrium as in: right atrium of the heart)
chamber from which blood enters the heart
(3) (meaning too rare to warrant focus)
Much less commonly, atrium can refer to anatomical structures other than the heart.