There are two large interior courtyards inside the National Gallery that one can view from any side or from the upper level. One contains a garden, one that often seems to evolve, a living and changing work of art.
Off this courtyard is an entrance to a space that is art in and of itself. The Rideau Chapel is the preserved chapel of a convent, carefully brought over when the place was to be demolished. Often when I visit, it is the sound of the interior that draws me in.
That sound is The Forty Part Motet, a sound sculpture concept by Janet Cardiff that deploys speakers around the chapel with choral music. The effect has to be experienced in person, but to sum it up, it feels like you're inside the music, that you can feel the sound. This time the speakers were set up inside.