Ai Weiwei: Yours Truly (2019)

While under house arrest in Beijing, Ai Weiwei remotely transformed Alcatraz, a former island penitentiary, into a remarkable expression of socially engaged art. Visitors could write messages of hope to the imprisoned activists featured in the Lego portraits. By the end of the exhibition, over 90,000 postcards were sent. Then, astonishingly, prisoners and their families began writing back.