All 3 Uses of

pantheon
in
The House of Hades

The room reminded her of the Pantheon in Rome, except this place had been decorated in Hades Modern.†
p. 536.2 *

As in the Pantheon, the domed roof was a waffle pattern of recessed square panels, but here each panel was a stela—a grave marker with Ancient Greek inscriptions.†
p. 536.4

At the apex of the ceiling, where the Pantheon's skylight would've been, a circle of pure black stone gleamed, as if to reinforce the sense that there was no way out of this place—no sky above, only darkness.†
p. 536.6

Definitions:

(1) (pantheon as in: pantheon of great writers)
a list of the most important of something -- such as great writers
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

More rarely, pantheon can refer to a list of all the gods of a religion. It can also refer to a building dedicated to those gods, or to a nation's heroes.

As a proper noun, Pantheon typically refers to an ancient Roman temple dedicated to all the Roman gods.