In this Symposium for the 2017-18 Mellon Sawyer we examine the expanded space of walls. Considering the dimensional spaces that walls define, create, inspire, and respond to, we will look at the role of walls in our cities and consider their social function as well as their form, how the two relate, and how works of art can inform or transform that relation. Walls divide us, but they can also form conduits for interaction and relation. From Chicago brick walls to the Great Chinese firewall, we look at how seemingly finite material artefacts can become generative actors in the built environment and give rise to new aesthetic forms in urban space. Speakers include Nadine Moeller, Wu Hung, Elizabeth Parke, and Rebecca Zorach.