This chapter examines megaproject design and planning in two “shrinking cities”- Philadelphia, PA and Detroit, MI- concludes that megaproject "metastasis", or repeated expansions into surrounding urban fabrics, is promoting the reduction of downtown into a series of self-contained enclaves. While political coalitions are constructing megaprojects, or large public works and/or single buildings, in cities around the world, in the United States, single-building megaprojects motivated by “growth coalitions” of public and private development actors have proliferated in downtowns since 1990. The urban design impacts of these megaprojects on the surrounding urban fabric have been little studied. Data on the institutional history, physical expan...