Resonant Room of Absolute Implicity
A room that records everything that is said inside of it. The space feels like a quiet, empty room with soft whisperings. When visitors put their head to the wall they can listen to the voices of past visitors, as well as to their own with some delay.
The atmosphere is a vast repository of everything that has ever been said; we could potentially rewind the movement of every molecule of air to recreate the voices of everyone who has spoken in the past.