The great Atrium seemed darker than Harry remem-bered it.
They had reached the Atrium.
Now, if you’ll just follow the Patronuses, you’ll be able to leave the Atrium.
"Level eight," said the witch’s cool voice, "Atrium."
The Atrium was full of people moving from fireplace to fireplace, sealing them off.
Harry thundered, and the powerful voice of Runcorn echoed through the Atrium: The wizards sealing the fireplaces froze.
If they emerged into the Atrium with a silver stag, and otter soaring alongside it, and twenty or so people, half of them accused Muggle-borns, he could not help feeling that they would attract unwanted attention.
There are no more uses of "atria" in the book.
Show samples from other sources
A bustling crowd of men and women—many of whom clutched rags to their mouths—filled a huge atrium topped with a glass ceiling far above, letting in loads of sunshine.
James Dashner -- The Death Cure
On Thursday, he was in the atrium of Scales Center after my class.