Breathtaking!! One visit is not enough to soak it all in.. I attended mass (in French) although I understood none of it, the experience to sit amidst such grandness while listening to the organs play..is unparalleled.
Guided tours are included in the entry fee $6 and are worth taking. Photography is allowed but the pics do no justice.
They also have a sound and light show "Aura"which I hear is good...A rather surreal place indeed!