This is a permanent exhibit in the Phoenix Art Museum by a Japanese artist named Yayoi Kusama. This picture is the best I could find though it doesn't really do the artwork justice.
The piece consists of a rectangular room with the doorless entrances enclosed in light-blocking antechambers. The room itself has mirrored walls and ceilings, and the floor is made of a reflective black surface. From the ceiling hang hundreds of different strands of LED lights that twinkle, glow, and change color. The effect of this on the viewer is total disorientation, and the artwork itself is physically difficult to escape.
A poor video of the artwork can be found here.
I think that this is beautiful because the nature of the piece is the engagement between the artwork and its audience. The audience itself is physically inseparable from the actual artwork.