The nearly completed Broad museum in downtown Los Angeles resembles a giant, milky honeycomb, so it was appropriate that on Sunday the place buzzed with activity.

Curious artists, journalists and art world figures streamed through the airy, light-filled space for a one-day sneak peek inside the museum, which is not scheduled to open until Sept. 20. A freight elevator, still lined with plywood, deposited arrivals onto the museum's top floor, a 35,000-square-foot space not yet broken up by partition walls.

A sound installation by Swedish artist BJ Nilsen hummed and hissed, echoing under the soaring ceiling as shards of light leaked through 318 skylights, glimmering against bare concrete and unfinished wood.