WASHINGTON (AP) - A Chinese artist who helped design Beijing's Olympic Stadium and has also drawn scrutiny for his political activism is opening the first North American retrospective exhibition of his work in Washington.

Ai Weiwei is barred from leaving China after being detained without explanation for three months last year. So he can't attend the opening Sunday at the Smithsonian's Hirshhorn Museum.

Curators say artworks in "Ai Weiwei: According to What?" capture Ai's push for free expression and his questioning of authority. One photograph shows him giving the middle finger to the White House.

The show includes new works, including 3,200 porcelain crabs called "He Xie."