SAN FRANCISCO (AP) — China's best-known dissident artist has a new exhibit at the former island prison of Alcatraz that pays tribute to dozens of political prisoners and political exiles around the world.

Ai Weiwei (EYE' WAY'-way) is noted for pieces critical of the Chinese government. His Alcatraz exhibition features portraits in toy Lego bricks of 176 political prisoners and exiles. Crews in China and in San Francisco assembled the portraits on Alcatraz under Ai's direction using 1.2 million Legos.

The exhibit opens to the public Saturday.

Alcatraz was closed as a federal penitentiary in 1963 and is now overseen by the National Park Service, which helped arrange and host the exhibition.

Ai's art is known around the world. But he has irked authorities in China by using his works and online profile to draw attention to injustices and push for greater transparency.