This thesis is concerned with the social impacts of urban design. It responds to the extensive history of race-based and class-based exclusion in American cities and offers a critique of postmodern planning strategies that seek to encourage social diversity but often undermine it. The Braddock Metro Neighborhood in Alexandria, Virginia, encompasses the historic community of Uptown, at one time the largest African-American community in Alexandria. Uptown, like most African-American urban neighborhoods in the United States, has been shaped by the forces of racism, segregation, displacement, public housing, white flight, economic disinvestment, crime, historic districting, and - recently - redevelopment and gentrification. The Braddock Metro Neighborhood Plan, a small-area master plan for accommodating transit-oriented redevelopment while affirming neighborhood character and connecting diverse residents, serves as the foundational document for neighborhood redevelopment. Central to the Neighborhood Plan is the replacement of public housing projects with mixed-income communities. These communities, which accommodate an influx of middle-income residents while retaining a percentage of low-income residents, are expressing a new type of residential diversity in the neighborhood, particularly in terms of the spatial proximity of different social groups. Proponents of mixed-income communities cite the potential for the formation of Bridging Social Capital (i.e., benefits, such as improved educational or employment opportunities, shared via casual ties among residents of different social groups). However, researchers have observed self-segregation occurring among residents of mixed-income communities, suggesting that spatial proximity alone does not guarantee the mixture of different social groups. This thesis posits that social mixing in diverse neighborhoods depends upon the presence of carefully designed social spaces, and it offers a set of streetscape interventions intended to support the formation of Bridging Social Capital in the Braddock Metro Neighborhood. The selected site consists of two historic street segments that are not yet fully redeveloped or gentrified. Design decisions are grounded in a careful assessment of site conditions, including existing social conditions, and supported by academic research in history, sociology, urban planning, and social-space design theory. Precise, small-scale interventions engage edges, affirm site character, and encourage residents to linger, sense one another, and tolerate challenging conditions of diversity. Design elements also accommodate the City of Alexandria's guidelines for street safety, mobility, accessibility, stormwater management, and historic preservation. / Master of Landscape Architecture / This thesis is concerned with the social impacts of urban design. It responds to the extensive history of race-based and class-based exclusion in American cities and offers a critique of postmodern planning strategies that seek to encourage social diversity but often undermine it. The Braddock Metro Neighborhood in Alexandria, Virginia, encompasses the historic community of Uptown, at one time the largest African-American community in Alexandria. Uptown, like most African-American urban neighborhoods in the United States, has been shaped by the forces of racism, segregation, displacement, public housing, white flight, economic disinvestment, crime, historic districting, and - recently - redevelopment and gentrification. The Braddock Metro Neighborhood Plan, a small-area master plan for accommodating transit-oriented redevelopment while affirming neighborhood character and connecting diverse residents, serves as the foundational document for neighborhood redevelopment. Central to the Neighborhood Plan is the replacement of public housing projects with mixed-income communities. These communities, which accommodate an influx of middle-income residents while retaining a percentage of low-income residents, are expressing a new type of residential diversity in the neighborhood, particularly in terms of the spatial proximity of different social groups. Proponents of mixed-income communities cite the potential for the formation of Bridging Social Capital (i.e., benefits, such as improved educational or employment opportunities, shared via casual ties among residents of different social groups). However, researchers have observed self-segregation occurring among residents of mixed-income communities, suggesting that spatial proximity alone does not guarantee the mixture of different social groups. This thesis posits that social mixing in diverse neighborhoods depends upon the presence of carefully designed social spaces, and it offers a set of streetscape interventions intended to support the formation of Bridging Social Capital in the Braddock Metro Neighborhood. The selected site consists of two historic street segments that are not yet fully redeveloped or gentrified. Design decisions are grounded in a careful assessment of site conditions, including existing social conditions, and supported by academic research in history, sociology, urban planning, and social-space design theory. Precise, small-scale interventions engage edges, affirm site character, and encourage residents to linger, sense one another, and tolerate challenging conditions of diversity. Design elements also accommodate the City of Alexandria's guidelines for street safety, mobility, accessibility, stormwater management, and historic preservation.