Gigatechnologies are the largest engineered systems that humans create. Research in nanotechnology is transforming the fields of materials, medicine, energy, computing, and manufacturing in profound ways. At the opposite end of the size spectrum, science and engineering at the gigascale is fundamentally different than science at the nano-, micro-, macro-, and mega-scales, but scant attention has been devoted to the giga-sciences. Examples of gigatechnologies are regional electric power grids, networks of highways and roads, municipal water systems, and clusters of buildings that aggregate to form blocks, neighborhoods, and cities. Studying gigatechnology will allow us how to minimize the bad, and emphasize the good properties that emerge in our cities, leading to greater sustainability, resiliency, and prosperity.