Oh, was this at MoMA?
Yes, from a few years ago. It's an iron sculpture by Richard Sera at SF MOMA. It was on loan from Stanford University's Cantor Arts Center. And is now back at Stanford.
The space that it was occupying at SF MOMA, is now used to display Diego Rivera's Pan American Unity fresco mural, which is 22 feet high by 74 feet long. It's pretty amazing!