All 3 Uses of

atrium
in
White: The Great Pursuit

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 large public room leading to other rooms--often skylit and containing plants and/or water features

or in ancient architecture:

a roofless area of a building--such as the center of a Roman house or an entry courtyard surrounded by roofed columns in an ancient Christian church
(2) (atrium as in: right atrium of the heart)
chamber from which blood enters the heart
(3) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Much less commonly, atrium can refer to anatomical structures other than the heart.