Taking over four rooms of Alcatraz - the former military prison, site of Native American protests and now one of America's most famous national parks - Weiwei's seven site-specific installations aim to prompt visitors to consider the experience of police force, as well as the art as an act of conscience.

The Alcatraz exhibition, opening Sept. 27, will feature sculptures, sound installations and other mixed-media work scattered among various locations on the Northern California island.

Recently a new generation of natural "wanderers" embarked on a monumental task in Muir Woods, a national monument named in honor of America's most famous naturalist John Muir.

Endangered species transferred from creek to hatchery until habitat improves

Ai's Alcatraz show is a joint project of the National Park Service and the Golden Gate National Parks Conservancy, which oversee the penitentiary-turned-park, and the San Francisco-based For-Site Foundation, a nonprofit that commissions artwork in public places.