In Chicago, more than 10,000 city-owned lots currently sit vacant, concentrated within predominantly Black and brown communities. David Brown, a professor at the School of Architecture at the University of Illinois at Chicago, has been mapping these unoccupied spaces—and developing possible uses for them—for more than a decade, and presented his findings and ideas at the 2012 Venice Biennale, then at the inaugural edition of the Chicago Architecture Biennial in 2015. Now, as the latter biennial’s 2021 artistic director, Brown further expands upon his project, using it to inform the central theme of the fourth-annual event, titled “The Available City.” On view tomorrow through December 18, the biennial’s free, public programming will provide a view into what happens when designers team up with local groups to rethink how vacant space might be used to engage and empower urban residents.