(written from a Production point of view)
Referenced in the first draft script of the Star Trek: Enterprise episode "The Andorian Incident" (which had the working title "Incident at P'Jem"), the Hall of Katras was an area where katras were stored in a series of catacombs beneath the monastery at P'Jem. The hall contained dozens of Vulcan urns on shelves, arranged from floor to ceiling, and the katras were stored inside the urns. At one point in the script, T'Kosh referred to the room as "a mausoleum of spirits." The Hall of Katras was written out of the script by the time the final draft was submitted.
In "Awakening", a "set" of katric arks is said to have once been discovered at P'Jem.