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This thesis presents an investigation of a new three-dimensional urban form where walking distances are less than a half-mile and congestion is minimal. The car-free urban form investigated herein is a city composed of skyscrapers massively interconnected with skybridges at multiple levels. The investigation consists of optimizing space use arrangement, skybridge presence or absence, and elevator number to simultaneously minimize total travel time, skybridge light blockage, and elevator energy usage in the city. These objectives are evaluated using three objective functions, the most significant of which involves a three-dimensional, pedestrian-only, three-step version of the traditional four-step planning model. Optimal and diverse designs are discovered with a genetic algorithm that generates always-feasible designs and uses the maximum fitness function. The space use arrangements and travel times of four extreme designs are analyzed and discussed, and the overall results of the investigation are presented. Conclusions suggest that skybridges are beneficial in reducing travel time and that travel times are shorter in cities wherein space use is mixed vertically as well as horizontally.