Buildings were constructed so close to one another that it gave rise to “handshake architecture.”

Unidentified Acts of Design is an exhibition and series of eight films made for the 2015 Shenzhen Urbanism\Architecture Biennale

In just three decades, Shenzhen has grown from being a small fishing village of just 30,000 people into an economic powerhouse. It houses at least 11 million people today, many of them migrants from across China. (The count doesn’t include those living there undocumented). In that time, shopping malls have popped up and sleek skyscrapers have transformed the skyline—evidence of the city’s industrial success.

But hidden among the glimmering towers are more than 200 “urban villages,” neighborhoods that developed out of rural villages after Shenzhen was a made a Special Economic Zone in 1980. They’ve become homes for millions of migrants from the countryside seeking cheap rent.

As a recent video released by the Victoria and Albert Museum in London explains, urban villages are a form of “informal urbanization”—and until the early 2000s, they were never part of the city’s “urban master plan.” The video, which was first presented as part of a 2015 exhibit titled Unidentified Acts of Design, walks viewers through these villages.

The first generation of urban villages, built in the ‘80s, were constructed on 32-by-32-feet plots. They were two stories high and intended for private family use, Shenzhen-based urban ethnographer Mary Ann O’Donnell says in the video. As more migrants flocked to the city, usually without their children, urban villages transformed to provide more rental spaces.

This gave rise to a unique architectural form known as “handshake architecture.” Buildings constructed between 1992 and 2000 were placed so close to one another that neighbors could reach across the space and shake hands with their neighbors, says O’Donnell.