The Bullitt Center in Seattle, described as the world's greenest building, showcases groundbreaking sustainable architecture. Despite Seattle's cloudy climate, this six-story office building is self-sufficient in energy, water, and waste management, thanks to its solar-powered, rainwater-harvesting, and waste-treating capabilities. Built to last 250 years, it uses geothermal heat and maximizes natural light, embodying the potential for urban clean energy transformation.