Provisional, informal, guerrilla, insurgent, DIY, hands-on, informal, unsolicited, unplanned, participatory, tactical, micro, open-source—these are just a few of the words floating around to describe a type of interventionist urbanism sweeping through cities around the world. The fact that there are so many concurrent, competing names for these myriad citizen-led urban improvements suggests that they remain a phenomenon-in-the-making, ripe for analysis. With mayors’ conferences recently featuring sessions on “lighter, quicker, cheaper” tactics (the term of choice for placemaking experts at the nonprofit Projects for Public Spaces) as alternative recession-era approaches to urban revitalization, and with “social impact design” burgeoning into a veritable cottage industry that young designers and established firms alike are eager to join, the trend might in fact be close to a tipping point. The subtitle of Malcom Gladwell’s book, The Tipping Point: How Little Things Make a Big Difference, could just as easily be the tagline for Spontaneous Interventions, the exhibition of the U.S. Pavilion at the 2012 Venice Architecture Biennale.

On the most straightforward level, without overly complex theorizing, this movement is about action, about multitudes of individual responses to problems as small as the cracks on the sidewalk, or as ubiquitous as unsafe intersections, or as large as crater-sized vacant lots stalled by a depressed economy. Architects and designers are trained to observe and solve problems, as we know, and one cornerstone of their education is the studio class that challenges them to develop hypothetical solutions to real, local, social, or urban problems. Moving ideas off the drawing board and into the world is the tricky part. Spontaneous Interventions: Design Actions for the Common Good celebrates those who act, who take the initiative to transform problematic urban situations into new opportunities or amenities to be shared by the public, without waiting for clients or permission, and in some cases, risking fines or arrest. Rolling up one’s sleeves, personally bankrolling or finding creative sources of funding, using every tool at hand to network and form tribes, mobilizing for the sake of shared passions, and simply making things happen—these are the modi operandi of a new class of citizen activists who are changing the shape of cities today.

In researching projects for the exhibition, we found hundreds of examples even before we issued an open call in January, which itself yielded over 450 compelling self-initiated urban improvements. We narrowed our choice to 124—the maximum number we could fit in the 4,000-square-foot permanent American pavilion in the Giardini, the public gardens of Venice—though we wish we could have included many more. We were expansive in our consideration of what qualifies as a “spontaneous intervention,” including projects that encroach on the territory of art and graffiti, well aware that some acts are more about self-expression than tactics for long-term change. Our goal was to find a diversity of original projects that transform public urban space to better serve the common good, seeking those that would add up to a useful archive of actionable strategies that could be replicated in other cities facing similar problems.

The notion of the “common good” is mutable and subjective, to be sure—what’s good for some might not be for others—but in selecting projects we adhered to the idea of what is beneficial to the most people with respect to everyday needs. New bike lanes in New York City might irk drivers; guerrilla gardeners might be annoying squatters to property owners; culture-jamming billboard pranks might be classifiable as vandalism; and all of these acts might be gentrification by another name. But we believe that the positive impacts of our featured examples of hands-on city-making far outweigh the negative.