"Apparition de l'Eglise éternelle" is among Messiaen best known pieces, probably (at least) because it's one of the easiest to play and also one of the easiest to listen to, with its clear arch form and its great evocative power.
It evokes (subjective opinion) a huge and majestic stone vessel, first far (pp
0:00) in an infinite dark sky full of distant scintillating stars. The vessel gets closer (long crescendo from
2:24) and closer (
3:35) and now fills all the sky above us (sudden perfect triads from
4:09 ), and finally continues its majestic cruise and goes away gradually (from
5:05 ) , before fading away (
8:08 to the end) in the infinite dark sky.
I never had the opportunity to play the Apparition on a really big "true organ", but the powerful Aristide (St-Ouen) provides really strong sensations while playing this piece.